[单选题]
A jumper in the long-jum:,uz*il fdap, p goeslr(ktak- k w;hir/,z5 into the jump with a speed of 12 m/s at an angle ol/ t( za-h5w,kk rrk;if $20^{\circ}$ above the horizontal. How long is the jumper in the air before returning to the Earth?
A. $0.21 \; s$
B. $0.42 \; s$
C. $0.84 \; s$
D. $1.3 \; s$
