Given scientific fact as input, generate the question from this fact such that it can be answered from the input.

[EX Q]: Filter feeders called rotifers collect digestive and excretory wastes in cloacal bladder primitive organ.
[EX A]: Filter feeders called rotifers collect digestive and excretory wastes in what primitive organ?

[EX Q]: Destructive interference in waves occurs two troughs what things overlap.
[EX A]: Destructive interference in waves occurs when what things overlap?

[EX Q]: Hydrogen chloride is a covalent compound.
[EX A]:
What type of compound is hydrogen chloride?