Dikaryotisation (n + n) in Agaricus is brought about by Clamp connections, Somatogamy between two hyphae of different strains, Basidiospores, or Both A and B?

Agaricus is a genus of mushrooms. Its mature plant body consists of vegetative mycelium living in the soil and sporophore that produces spores after coming above the soil. The vegetative body of mycelium consists of two filamentous hyphae that arise from basidiospores. The hyphae are initially nucleated but later on two hyphae of + and - strain come into contact and nucleus from one passes into the other (somatogamy). The cell thus becomes dikaryotic. It divides by clamp connections to form dikaryotic mycelium. Thus the correct answer is option D.