Subjunctive

Question 1

Indoor air pollution can threaten the health of closely confined farm animals and the workers who tend them and perhaps as well impairs the quality of such farm products like eggs, poultry, and pork.
A. perhaps as well impairs the quality of such farm products like
B. perhaps as well impairs the quality of such farm products as
C. perhaps also impairs the quality of such farm products like
D. may also impair the quality of such farm products like
E. may also impair the quality of such farm products as

Answer 1

I WAS VERY CONFUSED BECAUSE I FELT THAT IMPAIR IS RIGHT EVEN THOUGH AIR POLLUTION IS SINGULAR

BELOW IS THE RULE -

With modal verbs, you use the base form of the main verb even if the subject is singular.

Following are correct usage:

Pollution impairs the quality…
Pollution perhaps impairs the quality… (perhaps is an adverb)
Pollution may impair the quality… (may, a modal verb is used)