If the cause of a sudden severe list or trim is negative initial stability, counter-flooding into empty tanks may __________.

Correct Answer: Option C — cause the unit to flop to a greater angle

If a vessel has negative initial stability (G above M), it is in an unstable equilibrium. Counter-flooding into empty tanks can create a free surface effect or shift the center of gravity further, causing the vessel to 'flop' to a greater angle of loll, potentially leading to capsizing.