Final answer:
Haploid cells are sex cells or gametes which have one set of chromosomes and must fuse during fertilization to form a diploid zygote that will develop into an organism through mitosis. Therefore , the correct answer options is a)
Step-by-step explanation:
Cells that have one of each kind of chromosome and are also known as sex cells or gametes are called haploid cells. These haploid cells, specifically male and female gametes, must undergo fertilization to form a diploid zygote.
This zygote contains two of each kind of chromosome, one set from each parent, and subsequently develops into an organism through the process of mitosis. The choices diploid, haploid, chromatids, and zygotic, relate to different aspects of cell division and genetic inheritance. A diploid cell (choice a) contains two sets of chromosomes. A haploid cell (choice b) contains a single set and is referred to when discussing gametes.
Chromatids (choice c) are the two identical halves of a chromosome that are present after DNA replication but before cell division. Lastly, 'zygoid' is not a standard term in biology; the correct term for a fertilized egg is zygote, a diploid cell formed by the union of two haploid gametes.