Answer:
The leaf broke loose from the gnarled branch. - simple
The child ran to greet the dog, and the teddy bear fell to the ground. - compound
While the moon was full, the wolves howled and the dogs slept. - compound-complex
I looked over my shoulder, because I had an eerie feeling. - complex
Explanation:
Compound sentence is a type of sentence that contains at least two independent clauses (have subject and a verb and make a complete thought) which are merged with a comma, conjunction or a semicolon.
Complex sentences is a type of sentence that consists of one independent clause and one or more dependent clauses (can not stand alone).
Simple sentence is a type of sentence that consist of just one independent clause.
Compound-complex sentence is a type of a sentence that consists of at least two independent clauses and at least one dependent clause.