[单选题]
A jet fighter plane is launched from a catapult on an aircraft eb+ vp 53q6hckcarrier.6elgz,cb: t:89mddlv It reaches a speed of 42 m/s at the end of the catapult, an:gl8dtmb: v6d9l ez c,d this requires 2.0 s. Assuming the acceleration is constant, what is the length of the catapult?
A. $16 \; m$
B. $24 \; m$
C. $42 \; m$
D. $84 \; m$