[单选题]
An object is thrown upward with a speed pf1vh yvx p/0rq 0c7kf k(1a:sof 18t8gnv1nf)7 za8 wylv4 m/s on the surface of planet X where the acceleration due to gravitnfg zw888y7n1l vtva) y is $3.5 \; m/s^2$. What is the speed of the object after 8.0 s?
