Myofibrils are . a) the basic contractile units of skeletal muscle tissue
b) the contractile proteins located within a muscle cell
c) the boundaries of individual sarcomeres
d) specialized contractile organelles found in muscle cells
e) none of the listed responses is correct.

Option B

Explanation:

Myofibrils are very fine contractile fibers which extends in parallel to the columns along the length of the striated muscles fibres.

They are made of thick and thin myofilaments because of which the muscles appear striped.

The thick filaments in the muscles are composed of actin along with two other muscle protein known as tropomyosin and troponin. They help in contraction of muscles.

a researcher conducts an experiment on the secretion of a particular hormone in mice. scientists inject mice with a substance that stimulates the production of the hormone. the scientists then test the levels of hormones produced by the mice. the tool used to measure the hormones consistently detects the levels at 10 points lower than the actual hormone levels in the mice. this tool makes measurements, but the measurements aren't .

explanation:

no u