Answer: A
Explanation: It makes the most sense because it isn't directly speaking about something, it is mainly summarizing the main idea. I'm not 100%, but that's the one I would choose if it were me. Hope I helped out a little!
C. They are pulled toward Earth by the force of gravity (and in Physics you would learn that the deceleration speed of gravity is -9.8m/s/s)
A man is 100,000 times larger in micrometers than the amoeba, since 17 micrometers is 0.000017 meters, and 1.7 meters is 1,700,000 micrometers