Since Garrett and Carter bought popcorn and drinks, we have to figure out how much money is 1 drink and 1 popcorn. I figured the best way is to figure out half of $12.50 because 2 drinks and 2 popcorn cost that amount of money. You divide $12.50 by 2 to figure out half of that amount. The quotient equals to $6.25.
An inertial reference frame is a frame of reference in which a body remains at rest OR moves with a constant LINEAR velocity. Answer choices A, C, and D are moving linearly at a constant rate and are all inertial frames of reference. Answer choice E is motionless, and is therefor an inertial frame of reference. Answer choice B is rotating at a constant rate. Rotation is not an inertial frame of reference.
Therefor, the answer is B.