Questions: Which muscle cell type has visible striations but is not under voluntary control?

The answer is the first one: cardiac.

Explanation for each option:

1. Cardiac: Cardiac muscle cells have visible striations and are not under voluntary control. They are found in the heart and are responsible for pumping blood throughout the body. The striations are due to the organized arrangement of actin and myosin filaments, similar to skeletal muscle, but cardiac muscle operates involuntarily.

2. Smooth: Smooth muscle cells do not have visible striations and are not under voluntary control. They are found in the walls of hollow organs, such as the intestines and blood vessels, and help move substances through these organs.

3. Skeletal: Skeletal muscle cells have visible striations and are under voluntary control. They are attached to bones and are responsible for body movements.

In summary, cardiac muscle is the type that has visible striations but is not under voluntary control.