Final answer:
A cell with a large number of ribosomes attached to its rough endoplasmic reticulum is most probably specialized in protein synthesis.
Step-by-step explanation:
If a cell has a very large number of ribosomes attached to its rough endoplasmic reticulum (RER), it is probably specialized to make Proteins. The rough endoplasmic reticulum is studded with ribosomes and is involved in the synthesis of proteins, which are later transported through the cell in small sacs called transport vesicles. These proteins may be destined for incorporation into the cell membrane, secretion outside the cell, or use within other cellular compartments.