Answer:
Step-by-step explanation:
To fix the run-on sentence, you can use any of the following options, depending on the intended meaning and the level of connection you want between the two statements:
He went to see a horror movie; it was really scary. (Use a semicolon to create a stronger connection between the two clauses while still separating them slightly.)
He went to see a horror movie, and it was really scary. (Use "and" to connect the two clauses, indicating that they are closely related.)
He went to see a horror movie, but it was really scary. (Use "but" to show a contrast between his expectation and the actual experience.)
He went to see a horror movie. It was really scary. (Split the run-on sentence into two separate sentences for clarity.)
He went to see a horror movie, which was really scary. (Use a relative pronoun "which" to join the clauses, indicating that the second clause provides additional information about the first.)
Each of these options helps clarify the relationship between the two statements and makes the writing more grammatically correct. The choice depends on your intended meaning and the flow of your writing.