The linear acceleration of piston of a reciprocating engine is

(a) \(\omega^{2} r[\cos \theta+\cos 2 \theta /(2 n)]\)

(b) \(\omega^{2} r[\cos \theta+\cos 2 \theta / n]\)

(c) \(\omega^{2} r[\sin \theta+\sin 2 \theta /(2 n)]\)

(d) \(\omega^{2} r[\sin \theta+\sin 2 \theta / n]\)

where \(n=l / r\).