Final answer:
A ball dropped from the top of a building exhibits linear motion, as it is only acted upon by gravity, accelerating straight down with no horizontal movement.
Step-by-step explanation:
When ball A is dropped from the top of a building, it exhibits a type of motion known as linear motion. This is because the ball is under the influence of gravity alone, causing it to accelerate downwards toward the Earth's surface without any horizontal movement involved. Therefore, the correct option is D. Linear motion.
To clarify further, projectile motion refers to the motion of an object thrown or projected into the air, like a football, where both vertical and horizontal forces act upon it, and air resistance is negligible. This is not the case for ball A, which is simply being dropped. The other options, A. Uniform circular motion and C. Simple harmonic motion, do not fit the description of a dropped ball as they involve circular paths and oscillatory motion, respectively.