What structural units perform muscle fiber contractions?

Question

These are choices that they gave me.

1. Actin
2. Myofibrils
3. Myofilaments
4. Sarcomeres

Answer 1

Sacromeres are the smallest unit of muscle which contracts. Myofibrils are "strings" of sarcomeres. Myofilaments are either thick or thin filaments, both are needed for contraction to take place.

Answer 2

Myofibrils are responsible for muscle contraction