Final answer:
Option A correctly uses the subordinate conjunction 'although' to combine two sentences, showing a contrasting idea without needing a comma. Option B requires a comma after the subordinate clause when it comes first.
Step-by-step explanation:
The correct way to combine the two sentences using the subordinate conjunction "although" is:
A. A monarch flies 2,000 miles to the home of its ancestors, although it has never been there before. Option A correctly uses the subordinate conjunction 'although' to combine two sentences, showing a contrasting idea without needing a comma. Option B requires a comma after the subordinate clause when it comes first.
This sentence correctly uses the subordinate conjunction "although" to introduce a contrasting idea to the main clause. This compound-complex sentence structure expresses multiple ideas in a single cohesive sentence. It's important to note that a comma is required after the subordinate clause when it precedes the main clause, as seen in option B, but is not used in option A because the main clause comes first.