Arocket rises with constant acceleration to an altitude of 85 km , at which point its speed is 2.7 km/s .

In order to answer that question, we would need to know something about the rocket's climb.

Any of these would do it:

-- its speed when it reaches 85 km

-- its acceleration on the way up

-- the time it takes to reach 85 km.

a and c

c is 100% but i am confused in a