$\mathrm{A})$ Edible delicacies are Morels and Truffles in which Morels are spring mushrooms and they are quite expensive because of the very short growing period while Truffles are fruiting bodies of ascomycetes fungus which grow underground and they are also edible like mushrooms.

$\mathrm{B})$ For experimental genetics, Neurospora crassa is used because it is easy to grow and has a haploid life cycle.

$\mathrm{C})$ Penicillium, Streptomyces are good sources of antibiotics in which Streptomyces produce two-third of clinically useful antibiotics (kill or stop the growth of microbes) i.e.neomycin, bottromycin, chloramphenicol, capreomycin, etc. Penicillium produces an antibiotic i.e. penicillin.

$\mathrm{D})$ Rust is a plant disease that is caused by pathogenic fungi i.e.Ustilago while Smut is also a plant disease that is caused by Puccinia fungi and this disease is characterized by a large number of teliospores.

So the correct option is $\mathrm{C}$ .