The correct option is
B Two haploid cells without nuclear fusion
The sexual reproduction of fungi involves three phases, namely plasmogamy, karyogamy and meiosis.
In plasmogamy, there is a fusion of two protoplasts that brings together two compatible nuclei within the same cell. This pair of nuclei is called as a dikaryon (resulting cell becomes bi-nucleate).
Thus, there is fusion of two haploid cells without nuclear fusion.In case of lower fungi, plasmogamy is almost immediately followed by karyogamy but in higher fungi these two processes may be separated in time.
So, the correct answer is 'Two haploid cells without nuclear fusion'