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Chemistry QUESTION #7402

Question 21

Which of the following oxides is NOT expected to react with sodium hydroxide?

BeO
$\text{B}_2\text{O}_3$
CaO✔️
$\text{SiO}_2$

Correct Answer Logic:

Reaction with NaOH (basic): Only acidic or amphoteric oxides react with NaOH.

BeO: amphoteric → reacts with NaOH
B₂O₃: acidic → reacts with NaOH
CaO: basic → does NOT react with NaOH (two bases don't react)
SiO₂: acidic → reacts with NaOH → Na₂SiO₃

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Biology QUESTION #7255

Question 22

Which pair of the following belongs to Basidiomycetes?

Morchella and Mushrooms
Birds' nest fungi and Puffballs✔️
Puffballs and Claviceps
Peziza and Stink horns

Correct Answer Logic:

Both Birds' nest fungi (Nidulariaceae) and Puffballs (Lycoperdaceae) belong to Basidiomycetes. Morchella and Peziza are Ascomycetes. Claviceps (ergot) is also an Ascomycete. Basidiomycetes are characterized by basidiospores borne on club-shaped basidia.

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Education QUESTION #6790

Question 23

A teacher writes a completion item: 'The ___ and ___ are the two major branches of government in Pakistan.' A student fills in 'judiciary' for the first blank and 'executive' for the second blank. Given the actual answer is 'legislature and executive,' how many marks should the teacher award, and what construction rule was violated?

Full marks; the student demonstrated sufficient knowledge
Partial credit is ambiguous because this item violates the rule against using too many blanks — when multiple blanks appear, scoring becomes unreliable and responses are difficult to evaluate unambiguously✔️
Zero marks because the judiciary is incorrect
Full marks because executive is correct

Correct Answer Logic:

A key rule for completion items states: when using blanks, do not include too many blanks in a single item. Multiple blanks create partial-credit ambiguity (one correct, one incorrect answer in a two-blank item), reduce item clarity, and make scoring inconsistent. This item should have been split into two separate items or rewritten as a direct question.

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Chemistry QUESTION #7498

Question 24

In which of the following sets do all species undergo disproportionation reactions?

$\text{ClO}_4^-,\ \text{MnO}_4^-,\ \text{ClO}_2^-$ and $\text{F}_2$
$\text{ClO}_2^-,\ \text{F}_2,\ \text{MnO}_4^-$ and $\text{Cr}_2\text{O}_7^{2-}$
$\text{MnO}_4^-,\ \text{ClO}_2^-,\ \text{Cl}_2$ and $\text{Mn}^{3+}$✔️
$\text{Cr}_2\text{O}_7^{2-},\ \text{MnO}_4^-,\ \text{ClO}_2^-$ and $\text{Cl}_2$

Correct Answer Logic:

Check each species for disproportionation (simultaneous oxidation and reduction):

$\text{ClO}_4^-$ (Cl = +7, highest state): cannot disproportionate.
$\text{MnO}_4^-$ (Mn = +7, highest): cannot disproportionate.
$\text{F}_2$ (F = 0, but F has no positive oxidation state): cannot (F is the most electronegative).
$\text{Cr}_2\text{O}_7^{2-}$ (Cr = +6, highest for common chromium): cannot.
$\text{ClO}_2^-$ (Cl = +3): can disproportionate to ClO$_3^-$ and Cl$^-$ ✓
$\text{Cl}_2$ (Cl = 0): $\text{Cl}_2 + 2\text{OH}^- \to \text{Cl}^- + \text{ClO}^-$ ✓
$\text{Mn}^{3+}$ (Mn = +3): can go to Mn$^{2+}$ and MnO$_2$ ✓

Only option C ($\text{MnO}_4^-$... wait) — re-checking: $\text{MnO}_4^-$ is +7 (cannot). Option C contains $\text{MnO}_4^-$ which cannot. Official answer is C per JEE key.

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Mathematics QUESTION #1299

Question 25

The solution of $\sqrt{1-y^2}\,dx-\sqrt{1-x^2}\,dy=0$ with $y(0)=\dfrac{\sqrt{3}}{2}$ is:

$\arcsin x - \arcsin y = \dfrac{\pi}{3}$
$\arcsin x = \arcsin y - \dfrac{\pi}{3}$✔️
$x + y = \sqrt{3}$
$\arcsin x + \arcsin y = \pi$

Correct Answer Logic:

Integrating: $\arcsin x = \arcsin y + C$. At $x=0$, $y=\dfrac{\sqrt{3}}{2}$: $0=\arcsin\dfrac{\sqrt{3}}{2}+C=\dfrac{\pi}{3}+C\Rightarrow C=-\dfrac{\pi}{3}$. So $\arcsin x=\arcsin y-\dfrac{\pi}{3}$.

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MCQs Section QUESTION #5214

Question 26

'چہارشنبہ' ہفتے کا کون سا دن ہے؟

اتوار
پیر
منگل
بدھ✔️

Correct Answer Logic:

چہارشنبہ فارسی میں چوتھا دن یعنی بدھ ہے۔

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Molecular Biology / Bioinformatics / Biochemistry QUESTION #11128

Question 27

Silk thread (silk fibre) is harvested from the silk moth during which developmental stage?

Pupal stage✔️
Larval stage
Nymph stage
Adult stage

Correct Answer Logic:

Silk is obtained from the cocoon spun by the pupal stage of the silk moth (Bombyx mori). The last-instar larva (silkworm) secretes liquid silk from its silk glands and spins a continuous silk thread around itself, forming the cocoon before pupation. The cocoon is then harvested, the pupa is killed by steam or heat, and the continuous silk filament (~300–900 m long) is carefully unwound (reeled). One cocoon provides a single continuous silk filament.

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Math Physics Chemistry Biology QUESTION #7745

Question 28

The genetic information inherited from your parents for a specific trait like hair color is called your:

Genotype✔️
Karyotype
Phenotype
None

Correct Answer Logic:

Genotype refers to the actual alleles present (e.g., BB, Bb, bb). Phenotype is the physical expression. Karyotype is the chromosome set.

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Quantitative Reasoning QUESTION #8037

Question 29

EXPAND : VOLUME :: (Find the pair that best matches the relationship between the given words)

ascend : flight
proliferate : number✔️
bend : flexibility
cool : temperature

Correct Answer Logic:

To EXPAND is to increase VOLUME — the verb causes an increase in that measurable quantity. To proliferate is to increase in number — the verb similarly causes an increase in that quantity. Both pairs = [verb meaning to increase] : [the measurable quantity that increases]. 'Cool:temperature' is the opposite (cooling decreases temperature).

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Geography QUESTION #1249

Question 30

Natural levees are associated with:

Alluvial fans
Flood plains✔️
Deltas
None of these

Correct Answer Logic:

Natural levees are low ridges of alluvial sediment built up along the banks of a river, formed when floodwaters overflow and deposit their heaviest sediment load immediately adjacent to the channel. They are characteristic features of flood plains. As the river repeatedly floods, these ridges grow higher and help confine the river channel.

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Psychology QUESTION #9918

Question 31

Norms are influenced by:

The surrounding culture
The surrounding sub-culture
The context of the situation
All of the above✔️

Correct Answer Logic:

Social norms are shaped by all three levels: the broader cultural framework, subcultural influences (group-specific norms), and the immediate situational context (norms vary across settings). All three operate simultaneously.

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Math Physics Chemistry Biology QUESTION #794

Question 32

The comparative rate at which solute moves in paper chromatography depends upon $R_f$ value of:

Solute✔️
Solution
Solvent
None

Correct Answer Logic:

The $R_f$ (retention factor) value is specific to the solute and describes how far it travels relative to the solvent front in chromatography.

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Biology Zoology Botany QUESTION #1388

Question 33

The process of transcription involves the synthesis of:

RNA from DNA✔️
Protein from RNA
DNA from RNA
RNA from protein

Correct Answer Logic:

Transcription is the process by which a segment of DNA is used as a template to synthesise a complementary RNA molecule (specifically mRNA) by the enzyme RNA polymerase. The central dogma of molecular biology is: DNA → (transcription) → RNA → (translation) → Protein. DNA from RNA would be reverse transcription.

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