What is amphimixis?
(A) A fusion of pronuclei of male gametes
(B) A fusion of pronuclei from male and female gametes
(C) A fusion of pronuclei of female gametes
(D) The development of somatic cell into an embryo

Hint: Sexual reproduction is the type of producing offspring by the fusion of male and the female gametes. The fusion of the gametes takes place in the process of fertilization.Zygote is the end product of the fertilization in which it develops into the embryo.

Complete step by step answer:
The word amphimixis is derived from the Greek word amphi and mixis which means blending. Pronuclei is defined as the haploid nucleus that is present in the egg or sperm which undergo fusion. At the end of the fertilization or amphimixis, the egg is converted into the zygote or the fertilized ovum. The fertilization takes place in four processes, it includes sperm preparation, sperm egg recognition and binding, sperm egg fusion and Activation of zygote.
 
The zygote grows to produce the new young one which is distinct from its parents but have the similar genetic characters to them.Hence amphimixis is also specified as the sexual reproduction that takes place as the fusion of the pronuclei from the male and the female gametes.

Thus, Option B is correct.

Note:
Amphimixis is the sexual reproduction where the apomixis or the automixisis a type of asexual reproduction which is totally opposite to the amphimixis. Automixis is the fusion of the nuclei or gametes from the same organism.