The number of C-atoms in second member of an ester is / are :
(1) 2                  (2) 3                      (3) 4                   (4) 5

Dear Student 

As ester constitutes a general formula RCOOR' ( here R= H or alkyl or aryl , R' = alkyl or aryl) i.e here minimum value R = H. So the first member of ester will have 2 carbons which is $HCOOC{H}_3$(formate ester). Hence second member of ester family will have 3 carbon atoms. 
The second member of ester is $C{H}_{3}COOC{H}_3$.
So, the correct option is (2).

Regards.