Concept:A gamete is the mature sex cell that fuses with another sex cell during sexual reproduction.
Explanation:In sexual reproduction, two mature sex cells are involved, and these cells are called gametes.
The male gamete is the sperm cell, while the female gamete is the ovum or egg cell.
Each gamete is haploid, so it carries only half the number of chromosomes needed for a new individual.
When the sperm fertilises the ovum, the resulting single cell is known as a zygote.
The zygote repeatedly divides and develops into an embryo.
Later, in animals such as humans, the embryo grows into a fetus.
Therefore, out of the given options, the matured sex cell that takes part in sexual reproduction is the gamete, not the fetus, embryo, or zygote.
Answer:A. Gamete