Consider the following statements regarding a high speed in-line engine with identical reciprocating parts with cranks spaced to give equal firing intervals:

1). All harmonic forces, except those which are multiples of half the number of cylinders, are balanced 2). Couples are balanced if the engine is symmetrical about a plane normal to the axis of the cranks shaft 3). In a four cylinder in-line engine, second and fourth harmonic forces are unbalanced whereas in a six cylinder in a six cylinder in-line engine, second, fourth and sixth harmonic forces are unbalanced Of these statements

(a) 1,2 and 3 are correct

(b) 1 and 3 are correct

(c) 1 and 3 are correct

(d) 2 and 3 are correct.