Answer:
Run-on sentences can sometimes be fixed by adding a word and sometimes by adding punctuation.
Step-by-step explanation:
Example:
I thought I heard an intruder I reached for my baseball bat.
Add a word: Because I thought I heard an intruder, I reached for my baseball bat.
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I was hungry so I drove to McDonald's.
Add punctuation: I was hungry, so I drove to McDonald's.