Question

when two different observers watch a moving object,

a. they always see different motion
b. both of them always see the same motion
c. both of them see the same motion as long as both of them are moving
d. they will see the same motionvif they are in the same reference frame

Answer 1

I say a for this type of question

Answer 2

They will see the same motion if they are in the same reference frame.

Else, the length will be contracted ( in direction of motion) so they will see different time of object passing through them.