Inertia is measured by:

Correct answer: d mass

When mass grows inertia grows, so the mass of a body is its measure of inertia.

Why the other options are wrong

• a work: Work does not measure inertia; the book gives mass as the measure of inertia.
• b acceleration: Acceleration is the rate of change of velocity; it differs with mass, but it is not the measure of inertia.
• c force: Force is what changes a body's state; it is not the measure of inertia.