Please help just real quick!!

suppose that the amount of algae in a pond doubles every 4 hours.if the pond initially contains 90 pounds of algae ,how much algae will be in the pond after 12 hours? 

the answer choices is: 
A) 720 pounds 
B)  360 pounds 
C)  1,440 pounds 
D) 114 pounds

4 answers

Is it C??
No.
90
4 hrs >> 180
8 hrs >> 360
12 hrs >> ?
It's 720
Right.