The answer to the blank is physical.
<span>Velocity tells you what speed a moving object travels at and in what direction.</span>
The correct answer is C , because the space is vacuum and his body can explode and for this reason, the astronaut need a special costum to be protected. It's the same on the moon, because there is no atmosphere
The ball can't reach the speed of 20 m/s in two seconds, unless you THROW it down from the window with a little bit of initial speed. If you just drop it, then the highest speed it can have after two seconds is 19.6 m/s .
If an object starts from rest and its speed after 2 seconds is 20 m/s, then its acceleration is 20/2 = 10 m/s^2 .
(Gravity on Earth is only 9.8 m/s^2.)