Amphimixis is development of an organism obtained through

1. Apogamy
2. Apospory
3. Fusion of gametes
4. Without fusion of gametes

The process of fusion between the haploid male nucleus and egg nucleus is known as amphimixis. It is also known as syngamy. The process is known as fertilization which leads to the formation of a diploid zygote. The zygote has double the number of the chromosome to that of haploid gametes. It leads to the recombination of character which causes variation. It is a mode of sexual reproduction.

So, the correct answer is option C.