The correct answer is option 'B' - UP, Bihar, and West Bengal.

The GAP (Ganga Action Plan) is a project initiated by the Government of India to clean up the polluted waters of the Ganga River. The plan aims to intercept and divert municipal sewage falling into the river from 25 large urban conglomerates in three states, namely Uttar Pradesh (UP), Bihar, and West Bengal.

Importance of the Ganga Action Plan:
- The Ganga River is considered sacred by millions of people in India and holds immense cultural and religious significance. However, over the years, the river has become highly polluted due to the discharge of untreated sewage, industrial effluents, and other waste materials.
- The pollution in the Ganga not only affects the health and well-being of millions of people who depend on it for drinking water and irrigation but also poses a threat to the rich biodiversity of the river.

Objectives of the Ganga Action Plan:
- The main objective of the GAP is to reduce the pollution levels in the Ganga River and restore its water quality to a satisfactory level.
- The plan aims to intercept, divert, and treat the municipal sewage generated by 25 major urban centers located along the Ganga River.
- It also focuses on controlling the discharge of industrial effluents and other pollutants into the river.
- The plan includes the construction of sewage treatment plants, sewage pumping stations, and sewage conveyance systems to effectively manage and treat the sewage before it is discharged into the river.

States covered under the Ganga Action Plan:
- The Ganga Action Plan focuses on three states - Uttar Pradesh (UP), Bihar, and West Bengal.
- Uttar Pradesh is the largest state in terms of population, and several major cities such as Kanpur, Varanasi, and Allahabad are located along the Ganga River in this state.
- Bihar is another state with a significant population living along the Ganga River, and cities like Patna and Bhagalpur are major contributors to the pollution in the river.
- West Bengal, with cities like Kolkata and Howrah, also contributes to the pollution load in the Ganga.

Conclusion:
The GAP (Ganga Action Plan) aims to clean up the polluted waters of the Ganga River by intercepting and diverting municipal sewage from 25 large urban conglomerates. The plan covers three states - Uttar Pradesh (UP), Bihar, and West Bengal - where major cities along the Ganga River are located. By implementing measures to treat and manage sewage and control industrial effluents, the Ganga Action Plan aims to restore the water quality of the river and protect the health and well-being of millions of people who depend on it.