The correct answer is Nucleus The part of a cell that controls the activities of the cell is the nucleus. The nucleus is a large membrane-enclosed organelle found in eukaryotic cells, which contains genetic material known as DNA (deoxyribonucleic acid). This is to say; prokaryotic cells lack a nucleus. The nucleus is, in fact, the largest organelle. It takes about 1/10th of the cell volume.
The nucleus controls activities such as growth, control gene expression, processing of pre mRNA, protein synthesis, reproduction, and metabolism using the genetic information of the cells. The nucleolus is the largest structure in a nucleus. It is the site for the synthesis of ribosomes.