The correct answer is: I just had my car keys now I can’t find them anywhere! Has anyone seen my keys?
What is a run on sentence?
A run-on sentence is a sentence that lack proper punctuation between two independent clauses/phrases.
- I just had my car keys
- Now I can't find them
- Has anyone seen my keys?
These are all independent clauses, which are sentences that could stand on their own as a sentence. To fix the run-on sentence in the question, adding proper punctuation is neccesary.
The last answer is the solution that best uses punctuation to separate the independent clauses.