Got a PM for this.
Actually
increase/increases is a non-issue here, since
increase is not used as a
verb in this sentence. Technically, it is called a
bare infinitive (the infinitive
to increase, without the word
to). Since the structure of infinitives is:
to + the basic form of the verb,
to increases is an
incorrect construct, because
increase is the basic form of the verb; hence, in the bare infinitive usage also,
increases would be
incorrect.
From an understanding perspective, the structure of the sentence is like this:
For years, employees have seen <prices> increase.prices would be a noun; similarly, instead of
prices, what is mentioned in this sentence is:
what they pay toward health care . So, the sentence is:
For years, employees have seen <what they pay toward health care> increase.Similar to:
Jack watched his friend play.
Jack watched his friends play.
People have seen <something> increase.
As is evident, it doesn't matter whether we have
singular (friend) or
plural (friends), the bare infinitive remains the same:
play.
p.s. I don't believe test takers need to
develop concept in bare infinitives. The reason I highlighted it was to make sure that it is understood that we
cannot analyze
increase from a
subject verb agreement perspective here, because
increase is
not used as a
verb here.