Question

a glowworm is not really a worm. it is a type of
a small fly that gives off light.
b bat that spins silk.
c butterfly that eats other bugs.
d spider that lives in caves.

Explanation:

Glowworms are not actual worms. They are bioluminescent insects, often a type of small fly - like larva or adult that emits light.

Answer:

A. small fly that gives off light