Answer: II & III only
Step-by-step explanation:
Run-on sentences, also known as fused sentences, occur when two complete sentences are squashed together without using a coordinating conjunction or proper punctuation, such as a period or a semicolon.
In sentence II, you need to use a coordinating conjunction in order to make it correct. So that sentence is supposed to be
“I go to the mall on Sundays, but my sister prefers to go to the movies.”
In sentence III, there is supposed to be a comma, followed by the coordinating conjunction “but.”
In sentence I, there is a period separating the two sentences, so that is correct.
so your answer would be II & III only.
