The process of fusion between male nucleus and egg nucleus is called as

The correct option is A Syngamy
The process of fusion between the haploid male nucleus and egg nucleus is known as syngamy. It is also known as fertilization which leads to the formation of a diploid zygote.

Triple fusion is the fusion of the male gamete with two polar nuclei inside the embryo sac of the angiosperm. The polar nuclei belong to the egg or female gamete. It forms a triploid endosperm which helps in the development of the seed.

Double fertilization mainly takes place in angiosperms where a two sperm cell fuses with a single megagametophyte. One sperm fertilizes the egg cell and the other sperm combines with the two polar nuclei of the central large cell of the megagametophyte. It is the combination of syngamy and triple fusion. Conjugation is the transfer of genetic material between bacterial cells by direct cell-to-cell contact. The donor bacteria has F factor which is also known as fertility factor. The F factor is transferred from one bacteria to other by a connecting link known as pilus. Thus, the correct answer is option A.