Which cell type in human lacks a nucleus? Which function would this cell be unable to carry out?

Solution:

Ans. Red blood cells in the human body lack nucleus. So, they are unable to carry out cell division. 

RBC develops from progenitor cells with nuclei but as red blood cells mature, they lose their nucleus completely. Nucleus is responsible for cell division but blood cells don't divide, they are produced by other cells within bone marrow. This is an adaptation which allows the red blood cell to carry more oxygen.