Which of the following is not a type of sentence?

A. Compound-complex
B. Simple
C. Complex
D. Simple-compound

My answer is A

No

http://grammar.ccc.commnet.edu/grammar/sentences.htm#sentence_types

The correct answer to the question is indeed A. Compound-complex. To determine the answer, you need to understand the different types of sentences.

A compound-complex sentence is a sentence that contains two or more independent clauses (compound) and at least one dependent clause (complex). It combines the elements of compound and complex sentences.

A simple sentence consists of just one independent clause, which means it has a subject and a verb and expresses a complete thought.

A complex sentence has one independent clause and at least one dependent clause. The independent clause can stand alone as a complete sentence, but the dependent clause cannot.

A simple-compound sentence is a sentence that is a combination of simple and compound sentences. It features at least two independent clauses joined by a coordinating conjunction.

By understanding the definitions of these types of sentences, you would be able to determine that compound-complex is not one of the options. So, your answer of A is correct.