Answer:
1.f 2.c 3.d 4.e 5.d 6.a
Step-by-step explanation:
The third sentence is the inertial law itself. Concentrate in understanding that, and you will understand everything. For example, planets move for billion years because there is no friction in space, which help to understand the second sentence. Mass and inertia is practically the same thing. That's what explain why heavy objects are harder to change its motion. But, if an object has an unbalanced force, the net force is not zero, and if there is no friction, the object will change its motion.