What is mass?

The amount of matter that makes up an object
The amount of force it takes to move an object
The size of an object
The weight of an object

The amount of matter that makes up an object

How is force related to acceleration?

Acceleration has no relationship to force.
Acceleration works in variable proportion to force.
Acceleration works in direct proportion to force.
Acceleration works in inverse proportion to force

Acceleration works in direct proportion to force.