Concept:Choose the verb phrase that forms a correct expression without repeating the preposition "of".
Explanation:The sentence already supplies the preposition "of" immediately after the gap, just before the word "fuel".
So the gap only needs the phrasal verb "ran out", not "ran out of".
When the existing "of" is attached, the complete expression becomes "ran out of fuel", which is correct.
If you choose option B, "ran out of", the sentence will contain two "of"s in a row, producing an ungrammatical phrase like "ran out of of fuel".
Option C, "ran out on", means to abandon someone, so it does not suit the idea of fuel being exhausted.
Option D, "ran on out", is not a standard English expression and is therefore invalid.
Thus, "ran out" is the only option that keeps the sentence grammatically correct and meaningful.
Answer:A. ran out