In India, the widespread arsenic contamination problem in certain regions is primarily due to which of the following reasons?

Introduction / Context:
This question examines environmental geography and public health issues in India. Arsenic contamination of drinking water is a serious problem in several regions, especially in parts of West Bengal and neighbouring states. Understanding the primary cause behind this contamination helps in designing better policies and in answering environment and geography based questions in competitive exams.

Given Data / Assumptions:

• The focus is on arsenic contamination in Indian conditions, especially in groundwater used for drinking and irrigation.
• Options mention overexploitation of coal, arsenopyrite, ground water, surface water and sea water irrigation.
• We assume natural geologic presence of arsenic in some aquifers.
• The question asks for the primary, most important reason for the problem.

Concept / Approach:
The key concept is the relationship between groundwater dynamics and geochemical mobilisation of arsenic. In many affected areas, arsenic is naturally present in sediment layers. When groundwater is heavily pumped through tube wells, it changes the chemical environment in the aquifer, leading to release of arsenic into the water. Therefore, human activity in the form of over extraction of groundwater acts as a trigger for an existing natural hazard.

Step-by-Step Solution:
Step 1: Recognise that arsenic contamination is mostly detected in tube well and hand pump water rather than in surface water bodies. Step 2: Understand that large scale drilling of shallow and deep tube wells for drinking and irrigation has significantly increased groundwater withdrawal. Step 3: Overexploitation of groundwater alters the oxidation reduction balance in the aquifer and can release arsenic from sediments into the water. Step 4: The problem is not primarily due to coal mining, arsenopyrite mining or sea water, which are not widespread activities in all the affected rural regions. Step 5: Therefore, the correct answer is overexploitation of groundwater in the affected areas.

Verification / Alternative check:
Environmental reports and government documents on arsenic affected districts in India repeatedly mention tube well proliferation as a major contributing factor. The pattern is that as more bore wells are installed for agriculture and domestic use, arsenic levels in groundwater rise. In contrast, there is no similar large scale link with surface water use or with coal mining in all such regions. This broader evidence supports the conclusion that groundwater over extraction is the primary driver.

Why Other Options Are Wrong:
Option A (Overexploitation of coal deposits) is wrong because coal mining is concentrated in specific mining belts, while arsenic affected regions include many agricultural plains where coal is not mined.
Option B (Overexploitation of arsenopyrite) is incorrect because arsenopyrite is not commercially mined and overused at the scale that would explain the wide spread rural contamination.
Option D (Overexploitation of surface water) is wrong because rivers and ponds are generally less affected compared to groundwater; in fact, surface water is sometimes recommended as a safer alternative.
Option E (Release of arsenic from sea water) is not supported by evidence; the major arsenic problems are inland, far from coastal areas, and arise from geologic sediments, not from sea water irrigation.

Common Pitfalls:
A common mistake is to assume that any pollution problem must come from mining or industrial activities, but arsenic contamination in India is mainly a natural geologic issue worsened by human groundwater use. Students should remember that not all environmental problems are industrial; agricultural and domestic water use can also trigger serious contamination when combined with sensitive geology.

Final Answer:
The arsenic problem in India is primarily due to overexploitation of ground water in the affected areas.