Question

protein synthesis is...
the process by which proteins are built in cells.
the process of using proteins to build rna in cells.
the process by which fat is made in cells.
the process of using proteins to build dna in cells.

Explanation:

Protein synthesis is the biological process where cells build proteins. It involves transcription (DNA to RNA) and translation (RNA to protein). The other options are incorrect: RNA is not built from proteins (it's from DNA), fat synthesis is a different process, and DNA is replicated from DNA (not built from proteins).

Answer:

the process by which proteins are built in cells.