We need to see our answer choices to check all that apply.
Answer:
<u>B. Lithium, because it has two energy levels with one electron in the second level.</u>
The answer about muscles is extensors
When cells communicate by the signaling process, one cell produces a signaling molecule that must be received by the signal receptor on or in the responding cell. Signaling molecules are often called ligands, a general term for molecules that bind specifically to other molecules (such as receptors).
