The cell membrane of a muscle fiber is called a
myofibril
sarcolemma
sarcoplasm
myofilament

The correct answer is sarcolemma.

Explanation:

Sarcolemma is a structure that surrounds each muscle fiber as if it were a membrane. It is a complex structure consisting of lipids, carbohydrates and proteins, being semipermeable to allow the passage of certain substances and prevent the passage of others. However, the passage of substances can be altered due to the presence of a large number of transport channels and proteins.

The muscle fiber is surrounded by a lipid membrane, which has a special cover of a mixture of the collagen and glycoprotein fibrils that help isolate muscle cells from each other. It presents a series of invaginations, called T-tubules (extensions of sarcolem), which extend until it is closely related to the endoplasmic reticulum (network of membranes within the cell through which proteins and other molecules move)

this age may represent the age of the earth's accretion, of core formation, or of the material from which the earth formed. this dating is based on evidence from radiometric age-dating of meteorite material and is consistent with the radiometric ages of the oldest-known terrestrial and lunar samples.