Select all that are true when a muscle fiber is at rest.

a. There is a charge difference across the sarcolemma.
b. There is a charge difference across the sarcolemma.
c. Sodium-potassium pumps are active.
d. Sodium-potassium pumps are active.
e. Calcium is stored in the sarcoplasm.
f. Calcium is stored in the sarcoplasm.
g. ACh receptors are open.

Options f and g

Explanation:

A muscle fiber at rest includes such characteristics that calcium ions have not been released and at still stored in the sarcoplasm (a form of ER). Its release will trigger muscle contraction. Another characteristics is that the acetylcholine receptors that binds the neurotransmitter acetylcholine are open i.e not yet bound to the neurotransmitter. Binding of the neurotransmitter to its receptor will trigger the release of calcium ion from the sarcoplasm thus initiating muscle contraction.