Final answer:
The underlined portion of the sentence is an adjective clause. The sentence punctuated correctly is 'I hope that you do not oversleep, or we will be late for school.' The sentence about telescopes and astronomy is complex, and the sentence about Halley's comet is simple.
Step-by-step explanation:
The underlined clause in the sentence "Doves, which are considered symbols of peace and beauty, are related to plain old pigeons" is an adjective clause. It provides additional information about 'doves' and is essential for specifying what kind of doves we are talking about. Therefore, the correct answer to the question is "b. adjective clause".
Regarding the correct punctuation of sentences, option "d. I hope that you do not oversleep, or we will be late for school" is punctuated correctly, with a main clause followed by a coordinating conjunction and another main clause.
The sentence "Even before telescopes were invented, humans were interested in astronomy" is a complex sentence because it consists of an independent clause "humans were interested in astronomy" and a dependent clause "Even before telescopes were invented". Thus, the correct answer is "c. complex".
Finally, "Halley's comet should return in the year 2061" is a simple sentence. It contains only one independent clause, and there are no other clauses to complicate the sentence structure, which makes the correct choice "a. simple".