Since each myofibril is attached at either end of the muscle fiber, when sarcomeres shorten, the muscle fiber

A) lengthens.

B) shortens.

C) strengthens.

D) weakens.

E) pulls from the middle.

When sarcomeres shorten, the muscle fiber SHORTENS.

Explanation:

A muscle fiber is made up of many myofibrils that are attached at either end, which are composed of repeating subunits called sarcomeres that are responsible for muscle contraction. There are two types of filaments that makes up myofibrils they include;

- thick filaments and

- thin filaments

These filaments form the overlapping layers of sarcomeres. The contraction of muscle occurs through sliding- filaments model in the sarcomeres. The sarcomere and the muscle fibre shortens in length during muscle contraction ,due to the thick and thin filaments sliding over each other. I hope this helps, thanks.