Final answer:
From the equation Fnet = ma, force is directly proportional to both mass and acceleration. This means that if you increase the force applied to an object, both its mass and acceleration will increase. Similarly, if you decrease the force, both the mass and acceleration will decrease.
Step-by-step explanation:
From the equation Fnet = ma, we see that force is directly proportional to both mass and acceleration.
This means that if you increase the force applied to an object, both its mass and acceleration will increase. Similarly, if you decrease the force, both the mass and acceleration will decrease.
For example, if you push a car with more force, it will accelerate faster. And if you push a car with less force, it will accelerate slower.
Therefore, in a practical sense, the answer is b) Force is directly proportional to acceleration.