Final answer:
The correct sentence that uses an adverbial clause to combine sentences 7 and 8 is: We floated through the bayous, marshes, and swamps; our cajun captain pointed out cypress trees, water lilies, and other varieties of swamp plants.
Step-by-step explanation:
The correct sentence that uses an adverbial clause to combine sentences 7 and 8 is:
We floated through the bayous, marshes, and swamps; our cajun captain pointed out cypress trees, water lilies, and other varieties of swamp plants.
An adverbial clause is a dependent clause that functions as an adverb to modify the main clause. In this case, the adverbial clause 'our cajun captain pointed out cypress trees, water lilies, and other varieties of swamp plants' provides additional information about the action of floating through the bayous, marshes, and swamps. The use of a semicolon in between the two sentences helps to clearly separate the two ideas while maintaining the connection.