I think c is the correct answer, but can you explain why?

ML 1. The function t = f(S) models the time, in hours, for a sample of water to evaporate as a function of the size S of the sample, measured in milliliters. What are the units for f"(S) ? (A) hours per milliliter f' (s ) h/ml (B) milliliters per hour f " ( 5 ) w /ml/ mb hours per milliliter per milliliter milliliters per hour per hour 2. 3