Question

The animal cell which does not possess the nucleus is
A. Egg of hen
B. White blood cell
C. Red blood cell
D. Nerve cell

Answer 1

Nucleus is a relatively large organelle controlling all the activities of the eukaryotic cells. Some cells have more than one nucleus e.g., a binucleate cell has two nuclei per cell (Paramoecium), while multinucleated ones have many nuclei (Opalina). However, some cells lack a nucleus (anucleate) at maturity.

Complete answer:
In most of the mammals, red blood cells are biconcave in shape and are without a nucleus. Their unique shape relates to their function of transporting oxygen. As the red blood cells lack a nucleus and other organelles, it helps in providing more room for haemoglobin. Due to the absence of mitochondria, they respire anaerobically and do not use up any of the oxygen they carry. Due to the absence of a nucleus, they cannot divide as they do not have chromosomes.
Other options are correct because:

All the eggs have a nucleus
White blood cells/leukocytes possess multi-lobed nucleus at all the stages of life.
Nerve cells have a central nucleus in their cell body/ cyton.

Thus, option C is the answer.

Additional Information:
Along with mammalian Red blood cells, sieve tube cells also lack a nucleus.
A nucleus in a non-dividing phase is called an interphase nucleus and a typical interphase nucleus is differentiated into a nuclear envelope, nucleoplasm or nucleolus and chromatin.

Note:
Nucleolus is a spherical structure found in the nucleoplasm. It is not separated from the rest of the nucleoplasm as it is not bounded by a membrane. It is the site for ribosomal RNA synthesis. Thus, nucleoli are larger and more numerous in the cells that are actively involved in protein synthesis.