Which structure fuses to form a diploid zygote during sexual reproduction?

Answer:
the male and female gametes
Explanation:
they do this during sexual reproduction in order to form a zygote.
Answer:
Its the top one
Explanation:
In the gills of the mushroom cap, haploid nuclei fuse to form a zygote with 2 copies of each chromosome or a diploid cell. Meiosis occurs in the cells of the mushroom cap and produce haploid spores which complete the lifecycle.