Question

what is a valid frame of reference for observing motion if you are riding on a bus with a friend? a your friend sitting next to you b the bus driver at the front of the bus c objects like trees and houses outside the windows d the wastebasket on the bus

Explanation:

A frame of reference is a system for observing motion. When on a bus, your friend (a), the bus driver (b), and the wastebasket (d) are moving with you (same frame as the bus). Objects outside (c) are in a different frame (ground - based). But for your own frame (on the bus), your friend sitting next to you is a valid frame as you and your friend are at rest relative to each other (same velocity as the bus).

Answer:

a. your friend sitting next to you, b. the bus driver at the front of the bus, d. the wastebasket on the bus