It is a A. simple sentence, because there is only one main verb - opened.
A compound sentence has at least two independent clauses, a complex sentence has an independent clause and at least one dependent, a compound-complex clause sentence has two independent clauses and at least one dependent.
<span>Lillian will have been talking for two hours by the time she finishes her classical music lecture.
Let's assume that the underlined verb is "will have been talking." The underlined verb is in the tense of future perfect progressive. Because of the word will, it gives us the clue that it is future. Because of the line have been talking will give us the clue that it is perfect progressive.
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Your asnwer is A :) :) :) :)
