You will be given a definition of a task first, then an example. Follow the example to solve a new instance of the task.
In this task, you need to provide the correct option for a given problem on probability from the provided options.

Problem: in a throw of a coin find the probability of getting a tail ? 
Options: a ) 1 / 2 , b ) 1 / 3 , c ) 1 / 4 , d ) 2 / 5 , e ) 2 / 7
Solution: a
Why? "s = { h , t } e = { t } p ( e ) = 1 / 2 answer is a"

New input: Problem: a coin is tossed 4 times . what is the probability of getting exactly 3 heads ? 
Options: a ) 1 / 2 , b ) 1 / 4 , c ) 1 / 8 , d ) 1 / 16 , e ) 3 / 16
Solution:
b