In this sentence improvement question on English usage, consider the sentence He performed below par in the examination, where the underlined phrase below par is being checked for correctness as an idiom that describes poor performance. Choose the option that best improves or replaces the underlined expression while keeping the meaning that his performance was not up to the expected standard, and mark No improvement only if the given phrase is already correct.

Introduction / Context:
This question tests understanding of a common English idiom used to describe performance that is worse than expected. The sentence He performed below par in the examination uses below par as an idiomatic phrase. Many exam questions examine whether learners can recognise correct idioms and avoid being misled by similar looking but incorrect forms. The challenge is to decide if the phrase below par is already correct or if another option expresses the idea more accurately in standard English.

Given Data / Assumptions:

• The sentence describes a person's performance in an examination.
• The underlined expression is below par.
• The options are par below, poorly, below parr, and No improvement.
• The intended meaning is that his performance was not up to the usual or expected standard.

Concept / Approach:
The idiom below par originally comes from golf, where par is the standard number of strokes expected for a hole. In general English, below par now means worse than the usual or expected level, and it is widely used to describe health, performance, or quality. When an idiom is already correct, Exams often include misleading alternatives that look similar or offer simple synonyms, but idioms have fixed forms that should not be changed. Our approach is therefore to recognise below par as a correct idiom and avoid options that rearrange the words or alter the spelling.

Step-by-Step Solution:
First, understand that the sentence describes examination performance that did not meet expectations. Second, recall that below par is a recognised idiom meaning not as good as usual or not satisfactory. Third, examine each alternative and check whether any option improves clarity without breaking idiomatic accuracy. Fourth, notice that par below is not a known expression, and below parr is simply a misspelt version of par. Fifth, realise that poorly, while close in meaning, does not capture the full idiomatic flavour of the original, and the test is more likely to reward recognition of the correct idiom than replacement with a plain adverb.

Verification / Alternative check:
To verify, consider sentences like I am feeling below par today or Her performance this season has been below par. These are standard and common uses in newspapers, magazines, and conversations. Dictionaries list below par as an idiomatic phrase meaning not up to the usual standard. In contrast, par below does not appear as a standard phrase, and the spelling parr refers to a young salmon, which is clearly unrelated. Therefore, the safe and correct choice is to keep the original idiom unchanged and select No improvement.

Why Other Options Are Wrong:
Option A, par below, reverses the word order and destroys the idiomatic structure, making the phrase unnatural and confusing.

Option B, poorly, is a general adverb that expresses weak performance, but the question type specifically focuses on a sentence improvement problem where the original idiom is already correct; replacing it needlessly removes a natural and expressive phrase.

Option C, below parr, introduces a spelling error that changes the word into something unrelated to the intended meaning, so it is clearly wrong.

Common Pitfalls:
Learners sometimes over correct sentences because they expect every underlined part to be wrong, but exam setters often include items where the best answer is No improvement. Another pitfall is focusing only on meaning and ignoring idiomatic form, which leads candidates to choose a plain synonym even when a standard idiom is already accurate. Building familiarity with common idioms and trusting well known expressions can prevent these errors.

Final Answer:
The phrase below par is already a correct and natural idiom that means his performance was not up to the expected standard, so the correct choice is No improvement.