Given: Bacterial growth is stated to follow a law similar in form to radioactive decay, but for growth the number increases with time.
Find: Which graph best represents bacterial colony growth.
For bacterial growth, the number of bacteria at time t is given by
N(t)=N0ekt
where N0 is the initial number of bacteria and k is the growth constant.
So,
N0N=ekt
This means N/N0 increases exponentially with time.
Therefore, the correct graph must show an upward-curving exponential increase as time increases.

Thus, the correct option is A.