[单选题]
A jumper in the long-juuc7w)x 1w -nsmmp goes into the jd t6fhkx2d 8+wd szi+/fk: 8su5:iwc uump with a speed of 12 m/s at an angle of + idd/ i+u8stw6kudzfhw :28:fcsxk5 $20^{\circ}$ 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. $1.3 \; s$
