In the sentence “In this particular job we have discovered that to be diligent is more important than being bright”, which replacement of the underlined part gives the best grammatical improvement?

Introduction / Context:
This is a sentence improvement question that focuses on parallel structure and grammatical correctness. The original sentence reads: “In this particular job we have discovered that to be diligent is more important than being bright.” The underlined portion creates an imbalance because it mixes “to be diligent” with “being bright.” The task is to select the option that best corrects this imbalance while preserving the intended meaning.

Given Data / Assumptions:

• Original sentence: “In this particular job we have discovered that to be diligent is more important than being bright.”
• The underlined part is “to be diligent is more important than being bright.”
• Options change this clause in different ways.
• The meaning should remain that diligence is more important than brightness for the job.

Concept / Approach:
Good English style prefers parallel grammatical forms when comparing two qualities. In the original, “to be diligent” is an infinitive phrase, and “being bright” is a gerund phrase. Mixing these two forms in a direct comparison is awkward. One clean solution is to use the same form on both sides of the comparison, such as “being diligent is more important than being bright.” This keeps the verb form consistent and makes the sentence smoother and more correct.

Step-by-Step Solution:

Step 1: Identify the core comparison: diligent versus bright as qualities relevant to the job. Step 2: Notice that the original uses “to be diligent” on one side and “being bright” on the other, which breaks parallel structure. Step 3: Check option C: “being diligent is more important than being bright.” Both sides now use “being” plus an adjective, creating balance. Step 4: Confirm that this option preserves the intended meaning that diligence matters more than brightness. Step 5: Compare with the other options to see if any is grammatically or stylistically superior, which they are not.

Verification / Alternative check:
Option A, “for one to be diligent is more important than being bright,” still mixes “to be diligent” with “being bright” and introduces an unnecessary “for one.” Option B, “by being diligent is important than being bright,” is grammatically incorrect. Option D, “diligence is more important than brightness,” is grammatically fine but changes the structure more than necessary and shifts to abstract nouns. Option E claims no improvement is required, which is not correct, because the original sentence has non parallel verb forms. Option C fixes the parallelism clearly and keeps the tone natural.

Why Other Options Are Wrong:
Option A is wordy and keeps the original imbalance. Option B violates normal English structure because “by being diligent is important” is not a valid construction. Option D changes adjectives into nouns, which is acceptable but less faithful to the original construction of the clause underlined. Option E fails to correct the problem at all. Therefore, only option C both corrects the grammatical issue and preserves meaning in a concise way.

Common Pitfalls:
Some test takers choose the “no improvement” option because the sentence seems understandable. Others may choose option D simply because it sounds formal, without checking how far it moves away from the original wording. In sentence improvement problems, look carefully for parallel structures, subject verb agreement, and consistency in verb forms. When you see a comparison, check that both sides use similar grammatical patterns.

Final Answer:
The best grammatical improvement is “being diligent is more important than being bright.”