Final answer:
Cells with a single set of chromosomes are haploid cells. Somatic cells are diploid with two sets of chromosomes whereas gametes are haploid with one set.
Step-by-step explanation:
Cells that only contain a single set of chromosomes are considered haploid cells. Unlike somatic cells, which are diploid and contain two sets of chromosomes (46 in total, with 23 homologous pairs), haploid cells, such as gametes (sperm and egg cells), have just one set of chromosomes (23 individual chromosomes). The correct option for cells that only contain a single set of chromosomes is a) Haploid cells.