On the Basis of Data Collected During an Experiment, a Biologist

Multiple Choice

On the basis of data collected during an experiment, a biologist found that the growth of the fruit fly (Drosophila) with a limited food supply could be approximated by the exponential model where t denotes the number of days since the beginning of the experiment. ​
How fast was the population changing on the 20th day?

A) 18 flies/day
B) 15 flies/day
C) 14 flies/day
D) 17 flies/day
E) 16 flies/day