According to commonly cited environmental assessments Indias most polluted and least polluted states respectively are which of the following pairs?

Introduction / Context:
Environmental rankings sometimes compare Indian states based on levels of pollution, especially air quality and industrial emissions. Such rankings occasionally appear in current affairs questions, where candidates are asked to identify which state is among the most polluted and which is among the least polluted according to a particular study or survey.

Given Data / Assumptions:

- The question refers to Indias most polluted and least polluted states. - Four state pairs are given as options. - The wording suggests a specific comparative assessment used in general knowledge sources, not an exact up to the minute scientific measurement.

Concept / Approach:
Many general knowledge compilations based on earlier pollution studies describe Uttar Pradesh as one of the most polluted states due to high population density, traffic emissions and industrial activity. In contrast, Kerala is often cited as one of the least polluted states because of its relatively better air quality and higher forest cover in certain reports. The pair Uttar Pradesh and Kerala therefore matches the commonly quoted combination in older exam oriented material.

Step-by-Step Solution:
Step 1: Identify options that treat both parts of the pair as full states rather than mixing cities and states. Step 2: Notice that option c uses New Delhi, which is a city or union territory, making that pair less likely for a question framed about states. Step 3: Recall that Uttar Pradesh is frequently mentioned as heavily polluted in terms of particulate matter and industrial waste. Step 4: Remember that Kerala is often highlighted for comparatively better environmental indicators and cleaner air compared to many industrialised northern states. Step 5: Match this memory with option b, Uttar Pradesh and Kerala, and select it as the pair that fits commonly cited pollution rankings.

Verification / Alternative check:
Various media reports summarising pollution studies have described Uttar Pradesh as having a concentration of badly polluted cities, while Kerala appears infrequently in lists of highly polluted locations. Exam question banks that draw from these older assessments often present the pair Uttar Pradesh most polluted and Kerala least polluted as a memorisation fact. Therefore, even though actual pollution levels may change over time, this remains the expected answer in the context of this static GK question.

Why Other Options Are Wrong:
Uttarakhand and Rajasthan as a pair does not match the widely quoted combination of most and least polluted states in standard GK sources. New Delhi and Rajasthan is problematic because New Delhi is not a state and the question explicitly speaks about states. Uttar Pradesh and Uttarakhand pairs a highly polluted state with a relatively cleaner hill state, but this specific pair is not usually presented as the standard answer in question banks.

Common Pitfalls:
Students sometimes try to update such questions using the very latest pollution headlines, which can lead to confusion when older exam questions are based on earlier reports. For static GK it is better to focus on the combinations that are actually printed in question banks and guides. In this case, remembering Uttar Pradesh and Kerala as a contrasting pair of pollution extremes helps quickly pick the expected option.

Final Answer:
In many commonly cited static GK references, Indias most polluted and least polluted states are given as Uttar Pradesh and Kerala respectively.