Answer : 
 and
 and 

Greatest common factor of 

If we are able to factor out 
 from each option then that would be our answer.
 from each option then that would be our answer.
Lets check with each options
(a)
 , we cannot take out 5.
, we cannot take out 5. 
(b)
 , We can take out common factor and it can be written as
, We can take out common factor and it can be written as 

(c) 
 , we cannot take out n^2 because we have only 'n'
, we cannot take out n^2 because we have only 'n'
(d) 
 , We can take out common factor and it can be written as
, We can take out common factor and it can be written as 

(e) 
 , we cannot take out 5 because we have 24
, we cannot take out 5 because we have 24
So answer is (b) and (d)