Final answer:
The sentence 'Sally lives with her parents, although she could afford her own apartment.' contains two ideas joined by a connecting word, 'although,' which is a subordinating conjunction showing contrast.
Step-by-step explanation:
The sentence that contains two ideas joined by a connecting word is: 'Sally lives with her parents, although she could afford her own apartment.' Here, the connecting word is 'although,' which is used to introduce a contrasting idea to the first part of the sentence. In this context, it functions as a subordinating conjunction, creating a complex sentence.
When revising sentences for proper comma usage, we must consider the function of conjunctions and the structure of the sentences they are connecting. In the provided example, the two clauses could each stand as sentences on their own; hence, they are connected by a comma and the conjunction 'although' to show the contrast between them.
This question deals with recognizing sentence structure and the use of conjunctions in complex sentences. An understanding of how to connect ideas with conjunctions is crucial for constructing clear and cohesive writing.