Answer:
Options (2) and (3)
Explanation:
If 'f' is an exponential function,
f(t) =

Or we can rewrite the function as,
f(t) =

Here 'r' = rate of increase in the population.
a = Initial population
If the rate is positive, population will be increasing [(1 + r) > 1]
If the rate is negative, population will be decreasing [0 < (1 - r) < 1]
For increase in the population b > 1
For decrease in the population 0 < b < 1
And initial population (a) should be greater than 0.
Therefore, Options (2) and (3) will be the correct options.