Answer: B: Exponential
Explanation:
lets look at the numbers. he starts from 32 and it gets halved every "interval" of time:
32, 16, 8, 4, 2, 1, 0.5, 0.25 ........
as you can see, at first the time drops quickly, and then it slows down, approaching 0, (but never getting there).
this is the telltale sign of exponential decay!