Potential at shell B is the sum of contributions from all three shells:

• From shell A (radius $a$, charge $Q_A = 4\pi a^2 \sigma$): potential at B (outside A) $= \frac{Q_A}{4\pi\epsilon_0 b} = \frac{\sigma a^2}{\epsilon_0 b}$
• From shell B (radius $b$, charge $Q_B = -4\pi b^2 \sigma$): potential at B $= \frac{Q_B}{4\pi\epsilon_0 b} = \frac{-\sigma b}{\epsilon_0}$
• From shell C (radius $c$, charge $Q_C = 4\pi c^2 \sigma$): potential at B (inside C) $= \frac{Q_C}{4\pi\epsilon_0 c} = \frac{\sigma c}{\epsilon_0}$

$V_B = \frac{\sigma}{\epsilon_0}\left(\frac{a^2}{b} - b + c\right) = \frac{\sigma}{\epsilon_0}\left(\frac{a^2 - b^2}{b} + c\right)$

Cultural shock is a significant barrier to communication. It refers to the anxiety, disorientation, and communication breakdown that occurs when individuals are suddenly immersed in a cultural environment whose norms, values, and expectations differ radically from their own. It is not merely “excitement” or “curiosity” — it is a genuine psychological stress response. The textbook illustrates this with examples like families from conservative Muslim cultures moving to Western countries, where gender mixing in schools, co-educational institutions, and different social norms create communication crises. Cultural shock is distinct from acculturation (Option D), which is the gradual, successful adaptation to a new culture. Cultural shock is the resistance to or inability to adapt, resulting in a failure of communication at the most basic level.

We need $0 < st < 1$, which means $st$ is positive and less than 1.

Check each statement:

I. $s < -1$ and $t > 0$: If $s < -1$ (negative) and $t > 0$ (positive), then $st < 0$ (negative). This violates $st > 0$. ✗

II. $s < -1$ and $t < -1$: Both negative means $st > 0$ ✓. If $s = -2$ and $t = -0.4$, then $st = 0.8$, which satisfies $0 < st < 1$ ✓

Actually, wait. Let's reconsider: if $s < -1$ and $t < -1$, then both are less than $-1$, so both magnitudes are greater than 1. The product would be greater than 1, violating $st < 1$. Let me recalculate: if $s = -1.5$ and $t = -0.5$, then $st = 0.75$, which works. But $t = -0.5$ does not satisfy $t < -1$. If both $s < -1$ and $t < -1$, then $|s| > 1$ and $|t| > 1$, so $|st| > 1$, meaning $st > 1$ since both are negative (making product positive). This violates $st < 1$. ✗

III. $s > -1$ and $t < -1$: This gives us $-1 < s$ and $t < -1$. If $s$ is positive (satisfies $s > -1$) and $t$ is negative with $|t| > 1$, then $st < 0$. ✗ If $s$ is negative with $|s| < 1$ (like $s = -0.5$) and $t < -1$ (like $t = -1.5$), then $st = (-0.5)(-1.5) = 0.75 > 0$ and $< 1$ ✓

Actually, I need to reconsider option I more carefully...

Endospores are formed by Gram-positive bacteria like Bacillus and Clostridium. Mycobacteria are acid-fast; most Gram-negative do not form endospores.