The correct answer is option B: over. Here's the detailed explanation:
- The phrase "jumped over" indicates that the thief jumped and crossed the wall.
- The word "over" implies that the thief cleared the wall by jumping above it.
- The word "on" is incorrect because it suggests that the thief jumped and landed on top of the wall, which is not consistent with the idea of fleeing.
- The word "in" is incorrect as it implies that the thief jumped into the wall, which is not a logical action.
- The word "under" is incorrect because it suggests that the thief went beneath the wall, which is not in line with the idea of fleeing.
In summary, the correct word to fill in the blank is "over" as it conveys the idea that the thief jumped and crossed the wall while fleeing.

Understanding the Correct Preposition
In the sentence "The thief jumped __________ the wall and fled," the correct preposition is "over" (option B). Here’s a detailed explanation of why this choice is appropriate.
Meaning of the Prepositions
- On: This suggests being on top of something, which does not fit the context of jumping.
- Over: This indicates movement from one side to the other, passing above an obstacle. When you jump over a wall, you are clearing the wall in a single motion.
- In: This implies entering a space, which does not apply when discussing jumping over a wall.
- Under: This suggests moving below something, which again does not correspond to the action of jumping.
Contextual Relevance
- The action of jumping implies a vertical movement. To jump "over" a wall means to leap above it, which is a typical scenario for someone trying to escape or evade capture, like a thief.
- The sentence conveys urgency and action, making "over" the most logical choice, as it describes the escape effectively.
Conclusion
The best option to fill in the blank is "over" because it accurately describes the action of jumping in relation to the wall. The thief is not merely being on, in, or under the wall; he is clearing it in his escape.