Answer: I believe it is C.
Step-by-step explanation: Because if you take 4 x 20 = 80
If I am wrong sorry.
The previous population was 14000.
Explanation
The population decreased by 35% since the last measurement. So the current population is less than the previous population.
current population=9100
previous population =x
current population is 35% less than the previous population x

The previous population was 14000.
The answer is 0.12 millimeters because if you multiplied the numbers it would give you 0.12 mm hope this is correct