Which type of molecules does the body use to build and repair muscle tissue?

lipids
carbohydrates
nucleic acids
proteins

The correct answer would be proteins.

Proteins are considered as building blocks of the body as they are essential for the existence of life and is found in all living organisms in the environment.

Proteins are formed from amino acids and are included in various functions such as structural support, movement, cellular communication (receptors, hormones et cetera are mostly protein in nature), metabolism (generally enzymes are protein in nature) et cetera.

Similarly, muscle tissue is also made up of proteins, specially actin and myosin. Hence, in order to build and repair the muscle tissue body uses proteins.