I guess A should be the the answer .
A) Because paper of all kinds is the biggest single component of municipal trash, many municipalities have tried recycling to reduce the cost of trash disposal. CORRECT Subject Verb Agree.usage of Have is also correct.
(B) Because paper of all kinds is the biggest single component in municipal trash, many municipalities tried to recycle so that the cost of trash disposal is reduced. Component In is UNIDIOMATIC
© Because paper of all kinds are the biggest single components in municipal trash, many municipalities have tried to recycle to reduce the cost of trash disposal. SUBJECT-VERB ERROR
(D) All kinds of paper are the biggest single components of municipal trash, and so many municipalities have tried recycling to reduce the cost of trash disposal. Sentence is wordy
(E) All kinds of paper is the biggest single component of municipal trash, so many municipalities have tried to recycle so that the cost of trash disposal could be reduced. SUBJECT-VERB ERROR