Here are the answers to your questions:
Question 1:
A) Which of the following describes a simple sentence?
Answer: a sentence that contains a subject and a verb and expresses a complete thought
Question 2:
A) Which features make up a compound sentence?
Answer: two or more independent clauses joined with a conjunction and a comma
Question 3:
A) Which option describes a complex sentence?
Answer: a sentence that contains one independent clause and at least one dependent clause
Question 4:
A) Which option best describes a compound-complex sentence?
Answer: two or more independent clauses and at least one dependent clause