Answer:
Option C.
Explanation:
The general form of exponential growth function is

where, a is initial values and b is growth factor, b>1.
The given function are




In functions 1,2, and 4 the values of b are 0.07, 0.44 and 1/2 respectively. The values of b are less than 1. It means they represent exponential decay.
In function 3, the values of b is 6, which is greater than 1. It means it represent exponential growth.
Therefore, the correct option is C.