[单选题]
A spaceship takes a nonstop journey to a pkfe- o69 i9+sb 5ighavlanet and returns in 10 uf( g-wwo; ay/hours according to a clock on the spaceship. If the speed of the spaceship is 0w ;/(wag-youf.80c, how much time has elapsed on the Earth?
A. $3.2 \; h$
B. $7.0 \; h$
C. $15 \; h$
D. $17 \; h$
