Consider the following statements:

The unbalanced force in a single-cylinder reciprocating engine is 1). equal to inertia force of the reciprocating masses 2). equal to gas force 3). always fully balanced Which of the statements(s) is/are correct?

(a) 1 alone

(b) 2 alone

(c) 1 and 3

(d) 2 and 3 .