Hello!
The answer is Gravity. Lets take a look at the options:
A. Nope, this would be if the shuttle was going horizontal.
B. Again, this would be if the shuttle was going horizontal.
C. Yes! This is the only force that is being overcome by using the rocket thrusts to move up.
D. No, the shuttle is using its thrust rocks to push against gravity.
I hope this helps! :)
