Answer:
The sentence above is a compound complex sentence (d).
Explanation:
A compound complex sentence has at least two independent clauses and at least one dependent clause. An independent clause is a sentence that represents a complete thought and as such can stand alone as a sentence. On the contrary, dependent clauses fail to do so because they do not represent a complete idea. In the sentence above, the independent clauses are the following ones: "My friend is excited for the concert" and "but she has to leave early". The dependent clause is "because she has to be home by 10:00" (see 1)
1. *Because she has to be home by 10:00 (dependent clause which cannot stand alone as a sentence)
My friend is excited for the concert (independent clause. It's grammatically correct when it stands alone as a sentence because it represents a complete thought).
