The close-set hair covering rat’s body is

The correct option is Pelage.

Step-by-step Explanation:

1. Understanding Pelage: The term pelage refers to the entire coat of hair, fur, or wool that covers the body of a mammal, including rodents like rats. In rats, this close-set hair provides insulation, thermoregulation, and protection for the skin.

2. Analyzing the Other Options:
- Vibrissae: These are the long, stiff, tactile whiskers located on a rat's face (around the muzzle) used for sensing the environment through touch.
- Pili tactiles: This is the anatomical term for tactile hairs, which are specialized hairs (like vibrissae) that serve sensory functions rather than general body coverage.
- Muzzle: This is the anatomical region of the face comprising the nose, mouth, and jaw, not the hair itself.

Therefore, the close-set hair covering the rat's body is collectively known as the pelage.