A Rock Is Dropped from Rest Off of a High

Multiple Choice

A rock is dropped from rest off of a high cliff on another planet, planet X. There is no atmosphere, and thus no air resistance, on planet X. At the end of 1 second, the rock is moving at a speed of 6 m/s. What is the rock's average speed during the entire first second [from t=0 until t=1 sec]?

A) 10 m/s
B) 5 m/s
C) 6 m/s
D) 0
E) 3 m/s