If later is was 100 million years ago, later b would be 200 million years ago (because it is 100millions years prior to a). And therefore layer c must b 300 million years ago.
Answer:
Stimulus
Explanation:
The answer is stimulus. In plural it would be stimuli.
The last one, wind blowing for a long time wont cause much wind, but if the wind is short and choppy, it will cause the waves to be choppy.