Problem $20.$ Feed$-$forward Control System Analysis

A feed forward control system has the block diagram shown below. All of the

process elements are defined by first$-$order transfer functions.

Which transfer function best describes the transfer function $G_f(s)?$

$($A$)G_f(s)=-\frac{K_d({}_{p}s+1)}{K_p({}_{d}s+1)}$

$($B$)G_f(s)=-\frac{K_d}{{}_{d}s+1}$

$($C$)G_f(s)=-\frac{K_p{K}_d}{{}_{p}s+1}$

$($D$)G_f(s)=-\frac{K_p{K}_d}{s({}_p+{}_d)}$