A Racecar, Traveling at Constant Speed, Makes One Lap Around $\pi$

Multiple Choice

A racecar, traveling at constant speed, makes one lap around a circular track of radius r in a time t. Note: The circumference of a circle is given by C=2πr.
-When the car has traveled halfway around the track, what is the magnitude of its displacement from the starting point?

A) r
B) 2r
C) $\pi$ r
D) 2 $\pi$ r
E) zero meters