Right answer is (b) Dikaryon is haploid nuclei formed due to fusion of two nuclei
The explanation: Dikaryon is formed due to karyogamy. Sexual cycle of fungi comprises of 3 main steps: Plasmogamy, Karyogamy and Meiosis. Fungus prefers sexual reproduction over asexual reproduction during adverse environmental conditions. Initially, the cytoplasm of both the cells fuse which is called plasmogamy and followed by fusion of nuclei to form a diploid zygote called dikaryon. Later dikaryon undergoes meiosis in order to produce haploid spores.