HELP ME A biologist studies bacteria growing in four different environments. Which

HELP ME A biologist studies bacteria growing in four different environments. Which results can be modeled using an exponential function?
A) The population grows by a fixed amount each day.
B) The population grows by a fixed percent each day.
C) The population increases by 20% of its initial population on the first day and 15% on the second day.
D) The population increases by 100 bacteria on the first day and 80 bacteria on the second day.