For a tip-it'll be under whatever lectures you had Murray Thompson for, he LOVES placenta and oocytes.
I would strongly suggest you become familiar with what the layers of a developing cell (ectoderm, mesoderm, endoderm) form into as they develop to.
From my memory, it's conceptus.
A is wrong because gamete is pretty much any thing that is a mature haploid cell that can undergo division.
C is wrong because you gotta be a zygote and an embryo before you're old enough (certain number of weeks) to be classed a foetus.
D is wrong because follicle just refers to a part of the female human reproductive anatomy, which is in the ovary, so the oocyte is not fertilised at this stage so it is wrong.