The answer is proletariat
I think it would be “who weren’t able to go on the field trip”
It is important to do so, if you don't do it you may fail..
The answer to your question would be that the subject of the sentence is "there" and the verb is "are". That is, the correct option would be B.
The existential there is the use of the expletive "there" in front of a verb (usually the copulative verb "to be") to assert that someone or something exists. In fact, the existential there has the status of a dummy subject fulfilling the grammatical but not the semantic function of the subject.
