I went to visit him, but _________, he left a minute ago. [ ]

A. in my surprise

B. to my surprise

C. I was surprised

D. to my surprised

宇航员在一行星上以速度v₀竖直上抛一质量为m的物体，不计空气阻力，经t秒后落回手中，已知该星球半径为R.要使物体沿水平方向抛出而不落回星球表面，沿星球表面抛出的速度至少是多大？