B.To gain financially by combining two peoples's labor
I don't see any underlined words in the sentence. However, I'll just post my answer based on my understanding.
Where there is water ⇒ subordinate clause
There are mosquitoes ⇒ independent clause
Independent clause is a complete sentence. It has a subject, a verb, and expresses a complete thought.
Subordinate clause is a dependent clause that starts with a conjunction. It also has a subject and a verb but it is dependent on the main clause.
