In Case of Balancing Problems Pertaining to Locomotives, the Resultant

In case of balancing problems pertaining to locomotives, the resultant unbalanced force is minimum when

A) Half of the reciprocating masses are balanced by rotating masses
B) 1/2 of the reciprocating mass are balanced by equivalent rotating mass
C) More than half of the reciprocating masses are balanced by rotating masses
D) Reciprocating masses are balanced half by equivalent opposite reciprocating masses and the balance by rotating masses
E) None of the above