what does inertia depend on?
A. Momentum
B. Speed
C. Shape
D. Mass

Hint: inertia is the property by which an object tends to stay at rest or motion, hence if a body is either at rest or at motion the factor that is going to affect the inertia the most is its mass. If an object is heavy ,its tendency to stop the object is more and hence it is more difficult to stop it or resist its motion.

Complete step by step answer:
Imagine that there is a book being thrown at you and another a sheet of paper being thrown at you with the same speed. Which one do you think would you easily catch? The answer would surely be the sheet of paper, let’s see why.
Inertia is the tendency to keep an object in its current state. Thus the sheet of paper being lighter would require less tendency to stop its motion than a heavy book. In short, heavier the object, heavier will be the tendency to change its state of motion.
Hence it is clear that inertia definitely depends on mass.

So, the correct answer is “Option D”.

Note: It is mentioned that mass is the measure of amount of inertia.
Inertia also depends on the density of an object.
Inertia is directly proportional to mass.