Final answer:
Subordinate clauses can be classified as adverbial, noun, or relative clauses, each serving different functions in a sentence to add detail or information related to time, condition, or additional description.
Step-by-step explanation:
Each subordinate clause can be identified as a noun, adverbial, or relative clause. The clause "When Olivia returned from her week-long summer vacation" is an adverbial clause, describing when the flowers wilted. The clause "whatever college he chooses to attend" functions as a noun clause, as it is the object of what Joe's parents will be happy with. "that Halley's Comet appears once every seventy-six years" is another noun clause because it serves as the direct object of the verb 'know.' The clause "that I took in college" is a relative clause, giving additional information about the Chinese conversation classes. The clause "Although you protest" is an adverbial clause, indicating a condition. Lastly, "who graduated as valedictorian" is a relative clause, modifying the noun 'student.'