Improve the bracketed part of the sentence by choosing the correct future perfect form: By 2030 India (would) have become the most populous country in the world.

Introduction / Context:
Tense and modality questions frequently appear in competitive English exams. This item checks whether the learner knows how to form a correct future perfect tense when referring to a situation that will already be true by a certain time in the future. The sentence talks about India's population status by the year 2030, which calls for precise use of auxiliary verbs.

Given Data / Assumptions:

Sentence: "By 2030 India (would) have become the most populous country in the world."

Bracketed word: "would" is the part that has to be tested and possibly replaced.

We are referring to a prediction about a future state that will be completed by a specific year.

The options are "will", "should", "shall", and "no improvement".

Concept / Approach:

The future perfect tense is typically formed with "will have" plus the past participle.

"Would have" is often used to talk about imaginary past situations or future from a past viewpoint, not a neutral future prediction.

"Should" and "shall" express duty, suggestion, or formal obligation, and are not standard for neutral predictions of this type.

Therefore, we expect the appropriate form to be "will have become".

Step-by-Step Solution:
Step 1: Recognise that the phrase "By 2030" sets a definite future point. Step 2: When describing a state that will already be completed by that future time, we use the future perfect tense: "will have become". Step 3: Replace the bracketed auxiliary "would" with "will" so that the verb phrase becomes "will have become". Step 4: Check the full sentence: "By 2030 India will have become the most populous country in the world." This is grammatically correct and expresses a prediction about a completed state in the future. Step 5: Compare with the options and choose the one that gives the correct structure.

Verification / Alternative check:
If we use "would have become", the sentence sounds like speculation dependent on some condition, rather than a straightforward forecast. Using "should have become" suggests duty or expectation, which is not intended here. Therefore, "will have become" is the suitable standard for a neutral prediction about the future.

Why Other Options Are Wrong:
Option b, "should", would lead to "should have become", which expresses obligation or expectation and does not fit a neutral demographic projection. Option c, "shall", is traditionally used for first person future or formal instructions, so "shall have become" sounds unnatural with the subject "India" in this context. Option d, "no improvement", would keep "would have become", which is not the most accurate choice for this type of statement.

Common Pitfalls:
Students sometimes overuse "would" in future sentences because they hear it frequently in conditional or polite contexts. Another error is forgetting that "by" plus a future year usually calls for future perfect when the action will already be complete at that time. To avoid confusion, learners should remember that "will have" plus past participle is the typical future perfect pattern for neutral predictions.

Final Answer:
The correct answer is: will.