In this task, you need to provide the correct option for a given problem on probability from the provided options.

Example Input: Problem: in how many ways 4 boys and 4 girls can be seated in a row so that boys and girls are alternate ? 
Options: a ) 1152 , b ) 1987 , c ) 2012 , d ) 1856 , e ) 2546
Example Output: a

Example Input: Problem: a coin is tossed 3 times . what is the probability of getting exactly 2 heads ? 
Options: a ) 1 / 2 , b ) 1 / 4 , c ) 3 / 8 , d ) 5 / 8 , e ) 3 / 16
Example Output: c

Example Input: Problem: there are 4 books on a shelf , of which 3 are paperbacks and 6 are hardbacks . how many possible selections of 4 books from this shelf include at least one paperback ? 
Options: a ) a ) 40 , b ) b ) 45 , c ) c ) 50 , d ) d ) 55 , e ) e ) 111
Example Output:
e