Answer:
Option 2 -

Explanation:
To find : Which is an exponential growth function?
Solution :
Exponential growth function is defined as

Where b=1+r is the growth rate function or b>1.
Now we compare all the given functions,
1)

Here, b<1 so it a exponential decay function.
2)

Here, b>1 so it a exponential growth function.
3)

It is a linear function.
4)

Here, b<1 so it a exponential decay function.
Therefore, Option 2 is correct.