Final answer:
The boulder being pulled by the truck is moving at the same speed and direction as the tow truck, which is 35 mph to the east.
Step-by-step explanation:
The correct answer to the student's question on the motion of the boulder compared to the tow truck is: a. It is moving at the same speed and direction as the tow truck. Since the boulder is being pulled by the truck and there is no mention of any additional forces or speeds being applied to the boulder, we can infer that the boulder is moving together with the truck. This means that the velocity of the boulder is the same as that of the truck, which is 35 mph to the east.