In the following sentence, a part is to be improved. Four alternatives are given for the underlined portion. Choose the alternative that makes the sentence grammatically correct and more natural. In case no improvement is needed, choose "No improvement". The more they earn, more they spend.

Introduction:
This sentence improvement question tests your understanding of a common correlative structure in English: "The more..., the more...". This pattern is used to show a proportional relationship between two things, such as income and spending. Both parts of the comparison must be parallel and complete for the sentence to sound correct.

Given Data / Assumptions:
- Original sentence: "The more they earn, more they spend."
- The underlined portion in the exam is the second "more they spend".
- Options present different ways of structuring the entire comparison.
- We assume the intended meaning is "As they earn more, they spend more."

Concept / Approach:
In English, when we express a relationship of this type, we use the pattern "The more X, the more Y." The word "the" appears before both "more" words to signal that both parts are grammatically parallel. Leaving out "the" in the second part makes the sentence incomplete and unbalanced. Therefore, the best correction will restore the full structure "The more they earn, the more they spend".

Step-by-Step Solution:
Step 1: Identify the structure. The first clause is "The more they earn". The second clause should match this pattern.Step 2: Notice that in the original, the second clause is "more they spend", which is missing the article "the".Step 3: Look at option A: "The more they earn, the more they spend." This repeats the full pattern and sounds natural.Step 4: Option B, "More they earn, the more they spend", drops "The" from the first half, which is incorrect.Step 5: Option C, "More they earn, more they spend", drops "The" from both halves and is incorrect. Option D, "No improvement", keeps the original error. Thus, option A is the correct improvement.

Verification / Alternative check:
Try similar sentences: "The harder you work, the luckier you get", "The sooner we leave, the earlier we will arrive." In each case, "the" appears before both comparative forms. If you remove "the" from the second half, the sentence sounds incomplete: "The harder you work, luckier you get" is incorrect. This confirms that the same rule applies in the question sentence.

Why Other Options Are Wrong:
Option B breaks the symmetry by omitting "The" in the first clause. Option C omits "The" from both clauses, turning the sentence into two incomplete fragments. Option D suggests that the original sentence is acceptable, but it is grammatically flawed because it lacks the required parallel structure. Only option A follows the standard correlative pattern and retains clarity and balance.

Common Pitfalls:
Because the sentence is understandable even with the missing "the", some candidates may wrongly choose "No improvement". Others may try to shorten the sentence by dropping "the", not realising that this breaks a fixed pattern in English. To avoid such mistakes, remember that with comparatives like "more", "less", or "better" in this kind of proportional construction, the full pattern is "The more..., the more..." or "The less..., the less...".

Final Answer:
The best improvement is The more they earn, the more they spend.