The correct answer is option 'A', G.B. Nagar. G.B. Nagar, or Gautam Buddh Nagar, is a district in the state of Uttar Pradesh, India. It is located in the National Capital Region (NCR) and is known for its industrial and commercial activities.

- G.B. Nagar as the highest exporting district: G.B. Nagar has retained its position as the highest exporting district in Uttar Pradesh. This means that it has the highest volume of goods and products being exported to other regions or countries. This highlights the district's strong industrial base and its ability to produce and supply goods that are in demand globally.

- Factors contributing to G.B. Nagar's high exports: There are several factors that contribute to G.B. Nagar's high exports. These include:

1. Industrial infrastructure: The district has well-developed industrial infrastructure, including industrial parks, special economic zones (SEZs), and industrial clusters. These provide a conducive environment for businesses to operate and thrive, leading to increased production and exports.

2. Proximity to Delhi: G.B. Nagar's close proximity to the national capital, Delhi, gives it a strategic advantage. It allows businesses in the district to easily access the markets and transportation networks of Delhi, which is a major hub for trade and commerce.

3. Skilled workforce: G.B. Nagar has a skilled and educated workforce, which is essential for industries to operate efficiently and produce high-quality goods. The availability of skilled labor contributes to the district's competitiveness in the global market.

4. Diversified industries: G.B. Nagar is home to a diverse range of industries, including manufacturing, information technology, textiles, and automotive. This diversification allows the district to cater to different markets and meet the demands of various sectors, leading to higher exports.

- Impact of high exports on the district: The high exports from G.B. Nagar have a positive impact on the district's economy. They contribute to increased employment opportunities, foreign exchange earnings, and overall economic growth. The revenue generated from exports can be reinvested in infrastructure development, social welfare programs, and other initiatives that benefit the residents of the district.

In conclusion, G.B. Nagar has retained its position as the highest exporting district in Uttar Pradesh due to its strong industrial base, proximity to Delhi, skilled workforce, and diversified industries. The high exports from the district have a significant impact on its economy and contribute to its overall development.