Which of the following would involve primarily skeletal muscle activity?

A. scratching the ear with hind limb
B. movement of food down the intestines
C. heart pumping blood
D. urination

To determine which of the activities would involve primarily skeletal muscle activity, we need to understand the types of muscles in the body. There are three main types of muscles: skeletal, smooth, and cardiac.

Skeletal muscles are attached to the bones and are responsible for voluntary movements. They are under conscious control and allow us to perform various activities such as walking, scratching, or lifting objects.

Smooth muscles are found in the walls of organs and blood vessels. They are not under conscious control and are responsible for involuntary movements, such as the movement of food down the intestines and urination.

Cardiac muscle is only found in the heart and is responsible for pumping blood. It is also an involuntary muscle.

Given this information, we can eliminate options C and D since they involve smooth and cardiac muscles, respectively.

The correct answer would be A. Scratching the ear with the hind limb. This activity requires the use of skeletal muscles in the hind limb to perform the voluntary movement of scratching.