Complete the sentence "__number of (s) occur in amount of time?"

im pretty sure its b

a pan containing water is placed in a positio n where it is exposed to a 10 mile per hour wind. the pan contains a uniform depth of 1.27 cm of water, is quite wide, and has a length of 2.44 m in the wind direction. the water in the pan is at a constant temperature of 15.5 °c.

the answer is 0.42 is that is an option. this question provides no info