Improve the bracketed part of the sentence by choosing the correct option. If no improvement is required, select "No improvement". Sentence: The granaries of India are trapped in a dangerous vicious cycle of input use, where increased dumping of fertiliser in the wrong combinations (has rendered) the soil incapable of regenerating itself, which in turn escalates input use.

Introduction / Context:
This sentence improvement question checks your understanding of subject verb agreement and tense consistency in a complex sentence. The bracketed phrase has rendered describes the effect of increased dumping of fertiliser. You must decide whether this phrase is grammatically correct or whether one of the alternative verb forms expresses the idea more accurately.

Given Data / Assumptions:

• The full sentence is: The granaries of India are trapped in a dangerous vicious cycle of input use, where increased dumping of fertiliser in the wrong combinations has rendered the soil incapable of regenerating itself, which in turn escalates input use.
• The bracketed part is has rendered.
• Options: have rendered, is rendered, had render, and No improvement.
• The subject of has rendered is the noun phrase increased dumping of fertiliser in the wrong combinations.

Concept / Approach:
Two grammar points are central here. First, subject verb agreement: the head noun dumping is singular, even though it is followed by a prepositional phrase of fertiliser in the wrong combinations. Therefore, the correct auxiliary is has, not have. Second, tense consistency: the main clause uses a present tense are trapped and the later clause uses escalates, so the present perfect has rendered is suitable to describe a past action with present result, namely soil that is now incapable of regenerating itself.

Step-by-Step Solution:
Step 1: Identify the true subject of the verb in the clause where increased dumping of fertiliser in the wrong combinations has rendered the soil incapable of regenerating itself.Step 2: Recognise that dumping is the main noun, and of fertiliser in the wrong combinations is only a qualifier, so the subject is singular.Step 3: Match singular subject with singular auxiliary has, making has rendered the correct present perfect form.Step 4: Evaluate have rendered; it would wrongly treat the subject as plural and violates subject verb agreement.Step 5: Reject is rendered (simple present passive) and had render (incorrect structure; past perfect would be had rendered). Given this, the original has rendered is both grammatically and stylistically correct, so No improvement is the right choice.

Verification / Alternative check:
Read the sentence aloud with each option. With have rendered, the clause sounds odd because increased dumping is treated as plural. With is rendered, the meaning shifts to a general statement rather than a completed action causing a current state. With had render, the grammar is clearly wrong. In contrast, has rendered neatly connects past overuse of fertiliser to the present condition of the soil. This reading confirms that the original phrasing does not need correction.

Why Other Options Are Wrong:
Have rendered disagrees with the singular subject dumping and so fails the basic agreement rule. Is rendered switches to a simple present passive construction that does not fit well with are trapped and escalates in the surrounding context. Had render is ungrammatical; a correct past perfect structure would be had rendered, but that form is not even presented as an option. Therefore, none of these alternatives improves the sentence.

Common Pitfalls:
Examinees sometimes become distracted by nearby plural nouns like combinations and incorrectly think that they control the verb. It is essential to isolate the true head noun of the subject phrase when checking agreement. Another common mistake is to over correct by changing a perfectly fine present perfect form to another tense simply because the question asks for an improvement. Always test whether the original actually has an error before choosing an alternative.

Final Answer:
The bracketed phrase has rendered is already correct, so the best choice is No improvement, and option D is correct.