Find the Rate of Change of the Function $f ( x ) = - x + \cos x$

Multiple Choice

Find the rate of change of the function $f ( x ) = - x + \cos x$ .

A) $- \sin x + 1$
B) $\sin x - 1$
C) $- \sin x - 1$
D) $- \sin x - x$
E) $\sin x + 1$