Final answer:
The supertanker tied at the dock has more momentum because it has a larger mass.
Step-by-step explanation:
Both the supertanker tied at the dock and the falling raindrop have momentum, but the supertanker has more momentum.
Momentum is calculated by multiplying an object's mass by its velocity. Since the supertanker has a much larger mass than the raindrop, even if the velocity of the raindrop is higher, the supertanker will have more momentum.
Therefore, the correct answer is a. Supertanker tied at the dock.