The sentence that best connects the two ideas is the first one: The park benches need a new coat of paint, so we should volunteer to paint them.
This is a complex sentence since it includes two clauses: an independent clause and a dependent clause.<u> They have been joined by means of the conjunction "so" to indicate that benches sould be painted as a result of knowing that they need a new coat of paint</u>. <u>"So" indicates a cause-effect relationship</u>. On the other hand, the other option do not make any sense since the clauses have been joined by "however", an adverb that is used to indicate contradiction, and "although", a subordinating conjunction that connects ideas that contrast. <u>The clauses contained in this sentence do not present ideas that contrast nor express a contradiction</u>; therefore, a conjunction that indicates cause-effect relationship such as "so" must be used.
