A Child $C$ Pulls on a Wagon $W$ , Using a String $S$

A child $C$ pulls on a wagon $W$ , using a string $S$ ; the wagon moves forward at a constant speed as a result. The third-law partner to the forward force exerted on the wagon is which of the following forces?
( $\mathrm{R}=$ road.)

A) $\vec{F}_{T}^{S(W) }$

B) $\vec{F}_{T}^{\mathrm{W}(\mathrm{S}) }$

C) $\vec{F}_{T}^{\mathrm{W}(\mathrm{C}) }$

D) $\vec{F}_{T}^{\mathrm{C}(W) }$

E) $\vec{F}_{K F}^{\mathrm{W}(R) }$

F) Other (specify)