Which will form the embryo?

The female gamete is the egg cell or the ovum. The male gamete fuses with the female gamete and this is known as syngamy or fertilisation which results in the formation of a diploid zygote. Zygote is the first cell of the sporophytic generation. Zygote divides by mitotic divisions and forms a multicellular structure which is called the embryo. 

Thus, the embryo is formed by fertilised ovum.

So, the correct answer is C.