Hypothesis, a prediction based on what you know.
The correct answer is D. simple.
A simple sentence contains only one independent clause. If a sentence has more than one independent clauses, then it's called a compound sentence. If it has one independent clause, as well as one (or more) dependent clauses, then it is a complex sentence. A run-on sentence is a grammatically incorrect sentence which combines two or more independent clauses with a comma only, rather than with a conjunction.
