**Core concept**: Grammar (concessive clauses). **Analysis**: The sentence requires a subordinating conjunction to show contrast. **C. Although** is correct because it introduces a concessive clause (e.g., 'Although it rained heavily, the match continued'). **Wrong options**: - A. 'Because of' incorrectly implies causation. - B. 'Despite' requires a noun phrase (e.g., 'Despite the rain'). - D. 'However' is an adverb and cannot connect two clauses directly. **Key point**: Subordinating conjunctions (e.g., although) link dependent and independent clauses to show contrast.