In uredinales (rust fungi) basidia usually bearing how many numbers of basidiospores

Answer: Option B

In Uredinales (rust fungi) basidia usually bear four numbers of basidiospores.
A basidiospore is a reproductive spore produced by Basidiomycete fungi, a grouping that includes mushrooms, shelf fungi, rusts and smuts.
Typically, four basidiospores develop on appendages from each basidium, of which two are of one strain and the other two of its opposite strain.