Muscle fibers are directly surrounded by which thin layer of connective tissue?

The correct answer will be - epimysium

Explanation:

Epimysium is the fibrous connective tissue envelope which surrounds the muscle fibers of the muscle as a whole.

The epimysium plays an important role in maintaining the muscle structure as it protects the muscle from the friction caused by the associated bones and the muscles. The epimysium is continuous with other layers called the endomysium, perimysium, tendons and the fascia.

Thus, epimysium is the correct answers.