Sentence improvement: choose the correct preposition to complete "All the allegations levelled ___ the poor watchman were found to be baseless"

Introduction / Context:
This question tests sentence improvement by focusing on the correct preposition used with the phrase "allegations levelled". In English, certain verbs and expressions naturally combine with specific prepositions. Knowing these collocations is essential for natural and grammatically correct writing, especially in formal contexts like legal or official statements.

Given Data / Assumptions:

• The original sentence fragment is: "All the allegations levelled (over) the poor watchman were found to be baseless."
• The word "over" appears in brackets as the part to be improved.
• The options are "upon", "off", "against", and "no improvement".
• The sentence concerns allegations made about or directed at the poor watchman.

Concept / Approach:
The standard collocation in English is "to level allegations against someone". This phrase is widely used in news reports and legal language. The preposition "against" correctly conveys the idea that the accusations are directed toward a person. Other prepositions like "over" or "upon" do not naturally follow "level allegations". Therefore, the goal is to replace "over" with "against" to achieve idiomatic and grammatically proper English.

Step-by-Step Solution:
Step 1: Identify the core phrase: "allegations levelled ___ the poor watchman". Step 2: Recall standard usage: we say "allegations levelled against someone". Step 3: Test option A: "allegations levelled upon the poor watchman" sounds unnatural and is not a recognised idiom. Step 4: Test option B: "allegations levelled off the poor watchman" is clearly wrong; "off" does not fit here. Step 5: Test option C: "allegations levelled against the poor watchman" is standard and clear English. Step 6: Option D ("no improvement") would preserve "over", which is not the standard preposition for this phrase. Step 7: Conclude that "against" is the correct improvement.

Verification / Alternative check:
Look at how newspapers and legal documents describe accusations. You will commonly see sentences like "Serious allegations were levelled against the minister" or "Charges were brought against the company". In each case, "against" indicates the target of the accusation. Replacing "against" with "over" or "upon" would sound odd and non idiomatic. Therefore, "against" is the only acceptable choice here.

Why Other Options Are Wrong:
Option A: "Upon" is used after verbs like "rely upon" or "decide upon", but not after "level allegations". Option B: "Off" has meanings related to separation or removal and does not collocate with "allegations levelled". Option D: "No improvement" would keep an incorrect preposition, leaving the phrase unidiomatic.

Common Pitfalls:
A common mistake is to treat prepositions as interchangeable or to choose them based only on vague intuition. Many English phrases, especially in legal or formal contexts, use fixed preposition patterns that must be memorised. Another pitfall is assuming that "over" is correct merely because you see it in phrases like "argue over" or "dispute over", which are different constructions.

Final Answer:
The improved and idiomatic phrase is "allegations levelled against the poor watchman", so option C is correct.