Question

A run-on sentence

a. fails to express a complete thought and lacks proper punctuation b. is a dependent clause and lacks proper punctuation
c. combines two or more complete thoughts without proper punctuation
d. combines two or more dependent clauses without proper punctuation

Answer 1

The definition is: A run-on is a sentence in which two or more independent clauses (i.e., complete sentences) are joined without appropriate punctuation or conjunction.
Therefore the answer is: C?
It is up to you to choose the answer if you disagree with me but the definition is here. :P