The command to contract is distributed throughout a muscle fiber by the

The correct answer will be- Transverse tubules

Explanation:

Transverse tubules are the tubular structure formed by the extension of the plasma membrane which innervates the cardiac and skeletal muscle cells. The T-tubules structure is structured between 20-40 nm and located at the junction of the I and A band.

The signals from the motor neurons once raches the motor endplate in muscles are carried into the muscles by these T-tubules which transmits the signals to muscle cells at very high speed. The T-tubules cause the release of the Calcium ions from the sarcoplasmic reticulum that cause contraction of the skeletal muscle.

Thus, Transverse tubules are the correct answer.

the farther away the object is from the central star (the sun) it's gravitainal pull on the object is weaker when it is farther

explanation:

the answers are as following:

1. c. double helix, nucleosome, coil, supercoil, chromosome

2. b. g2 phase, preparation for mitosis

3. d. interphase consists of the g1, s, and g2 phases

4. c. metaphase

5. a. chromosomes are duplicated before cell division so that each new daughter cell has a complete set