Please help asap!!

Its A

We have this:

A  = 90 * (2)^(t/4)       where A is the amount present after  t hours

So...after 12 hours, we have

A  = 90 * (2) ^(12/4)

A = 90  *  (2)^3

A = 90 * 8

A =  720 pounds  =  "A"

We have 90*2*2*2, because it doubles every 4 hours, and 12/4=3, so 3 two's.

Thus, the answer is \(\boxed{720}\)