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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 farces, 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-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 2 are correct  

D) 2 and 3 are correct