Question

___________ is a structure that contains spores and is located on the underside of fern leaves.

Basidium
Bacillus
Cilium
Sorus

Answer 1

located on the lower surface of fern leaves. they’re essential for reproduction

Answer 2

The answer is "Sorus"
So it is D because
Sorus is a structure that contains spores and is located on the underside of fern leaves.