Answer:
The arrow labelled X is ribosome.
Explanation:
Ribosomes can be described as structures which are the protein manufacturing unit.
For a protein to form, The DNA forms mRNA by the process of transcription. The start and stops codons are attached to the mRNA and it travels outside the nucleus into the cytoplasm where ribosomes are present.
The ribosomes are the site where the process of translation takes places. The process of converting RNA into proteins is termed as translation.
