The correct answer is embryonic cells.
The embryonic cells are the cells present in the embryonic stage of the development of a fetus. The embryonic cells divide rapidly in order to make different cells present in the body and growth. So, these cells have a very short life span.
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The length of the cell cycle is increased after childhood, as the growth required is very less as compared to the embryonic life. The gametes (egg or sperm) fuse together, which result in formation of zygote, but before the formation of the zygote, the mature gamete cells do not divide.
