Final answer:
The captain's reference to 4-meter high waves corresponds to a wave height from trough to crest. The amplitude is half of this height, which means the correct amplitude of these waves would be 2 meters.
Step-by-step explanation:
When the fishing-boat captain mentions waves that are 4 meters high, he is referring to the wave height, which is the vertical distance from the trough to the crest of the wave. The amplitude of a wave, however, is defined as the maximum displacement of the wave from its equilibrium position (the still water mark) to the crest. Therefore, the amplitude of a wave is half of its height.
Since the wave height mentioned is 4 meters, the amplitude would be half of this, which is 2 meters. So when the captain says the waves are 4 meters high, he is probably talking of waves with an amplitude of 2 meters. The correct answer is B. 2 m.