The matured sex cell which takes part in sexual reproduction is referred to as

A.

gamete

B.

fetus

C.

embryo

D.

zygote

Correct answer is A

Gametes are reproductive cells (sex cells) that unite during sexual reproduction to form a new cell called a zygote. Male gametes are sperm and female gametes are ova (eggs).
Embryo is the stage of animal development in the uterus before the animal is considered a fetus. In humans this is equivalent to the first three months.