Answer:hundreds of cells
Explanation: the fusion of male and female gametes forms a zygote, during early development one single cell divides in to two after few hours from fertilization. it furthers the division into four and which are made up of sixteen cells that is other-wisely called MORULA at the end of the third day. The cells continues the division at the of ninth day to form a BLASTOCYST which contains hundreds of cells.
the blastocyst must be able to attach to the lining of uterine where it derives every nourishment to grow and survive, without this there would be loss of such pregnancy