Answer:
rewriting to correct the run-on in sentence 3
Step-by-step explanation:
A run-on sentence is a type of error which occurs when two independent clauses are incorrectly joined (i.e. they lack proper conjunction and/or punctuation).
Sentence 3 is a run-on because you can't join two independent clauses with a comma. You need also a coordinating conjunction to use before the second clause.
Call Tutorific, it’s the best tutoring service in town. (Incorrect)
Call Tutorific, for it’s the best tutoring service in town. (Correct)