Find out the alternative which will replace the question mark.
$$16:7::36:?$$

Let's find the logic connecting the first pair ($16:7$):
The first number is a perfect square: $16=4^2$.
The second number is obtained by adding $3$ to the square root of the first number:

$$\sqrt{16}+3=4+3=7$$

Applying the same logic to the second pair ($36:?$):
The first number is $36=6^2$.

$$\sqrt{36}+3=6+3=9$$

Therefore, the missing number is $9$.