The correct option is C Fertilisation
“Fertilisation” is the first step of reproduction, where fusion of sperm and ovum takes place. During fertilisation, the nuclei of the sperm and the ovum fuse to form a cell with a single nucleus, known as zygote.
Binary fission and budding are asexual modes of reproduction. Cloning is the production of an exact copy of a cell, any other living part, or a complete organism.