Name the structure that plays an important role in synthesis of protein.

Ribosome plays an important role in synthesis of protein.

Out of the given options, only ribosomes are organelles present inside the cell. Ribosomes are granules, majorly present on the rough endoplasmic reticulum. They are a site of protein synthesis in all active cells. The manufactured proteins are sent to various places for various functions depending on the need for example, formation of cell body, enzyme or hormone formation, wear and tear of tissues or other important cell/body functions.

The other options are incorrect, like the RNA is a molecule, and transcription and translation are processes.