[单选题]
A jet fighter plane is launc+32*jmij0 vq7x,*hlc hpn 5(sle atxahed from a catapuu q8 ,jhyl/1mmlt on an aircraft carrier. It reaches a speed of 42 m/s at the end of the catapult, and this requires 2.0 s. Assuming the acceleration is constant, what ishy1j,/ulmq m8 the length of the catapult?
A. $16 \; m$
B. $24 \; m$
C. $42 \; m$
D. $84 \; m$