We need $0 < st < 1$, meaning $st$ is a small positive number. This requires $s$ and $t$ to have the same sign.

• Option A: $s < -1, t > 0$ → $st < 0$. Not possible.
• Option B: $s < -1, t < -1$ → both negative, so $st > 0$. For example $s = -2, t = -0.3$: $st = 0.6$, which satisfies $0 < st < 1$. ✓
• Option C: $s > -1, t < -1$ → could give $st$ negative or positive depending on sign of $s$. If $s = 0.5, t = -2$: $st = -1 < 0$. Not valid for all cases.
• Option D: $s > 1, t < -1$ → $st < -1 < 0$. Not possible.

Option B is the one that can satisfy the condition.