What is a protein that is the main component of the thick filaments in muscle fibers and is responsible for muscle contraction?
a. actin
b. myosin
c. actin and myosin
d. nerve and bone

The answer is B.) myosin

Both protein molecules myosin and actin are responsible for muscle contraction but myosin is the main protein component of thick filaments whereas actin is the main protein component of thin filaments. Hope this helps.

its b

Explanation:

if the type of the food available changes, then the frequency of beak types will change, because birds with beaks more suited to the available food will be more successful over time.

bacterium is not correct