The correct answer is option A, a zygote 
Reason - 
A zygote (single diploid cell) divides over a period of three week time period and transforms into a larva. An embryo goes through the phases of stages like cleavage, gastrulation, neurulation and organogenesis. A larva transforms through the process of metamorphosis to develop into an adult drastic changes. 
The entire process of development is as follows – . 
Eggs, zygote, larva and then into an adult