Let's break down the terms:
Haploid: A haploid cell refers to a cell that contains a single set of chromosomes. In humans, haploid cells are the sex cells or gametes, such as sperm cells in males and egg cells in females. Haploid cells have half the number of chromosomes compared to the somatic cells in the organism.
Diploid: A diploid cell refers to a cell that contains two sets of chromosomes. In humans, diploid cells are the somatic cells, which make up the majority of the body's cells. Each somatic cell contains two copies of each chromosome, one inherited from each parent.
So, in summary, the correct answer (A. haploid; diploid) indicates that a haploid cell has only one set of chromosomes, while a diploid cell has two sets of chromosomes.