9. Which one of the following sentences contains two ideas joined by a connecting word?

A. Mike ran after the bus.
B. Tina arrived at work earlier than usual.
[C. Sally lives with her parents, although she could afford her own apartment.]
D. Frank went fishing on Saturday he caught many fish.

Correct.

The sentence that contains two ideas joined by a connecting word is option C: "Sally lives with her parents, although she could afford her own apartment."

To identify sentences that contain two ideas joined by a connecting word, you need to look for sentences that use coordinating conjunctions (connecting words) to link two independent clauses. In this case, the word "although" is a coordinating conjunction that connects the ideas of Sally living with her parents and her being able to afford her own apartment.