Let a be the number of bacteria after one hour.
From the table, we get a=33.
The difference between 57 and 33 is 57-33= 24.
The difference between 81 and 57 is 81-57=24
Hence we get the common difference d=24.
The given data is in the arithmetic progression.
The formula for the nth term in the arithmetic progression is
Substitute a=33 and d=24, we get
Hence the required recursive equation is
Option A is correct.