Explanation:

- The National Bank for Agriculture and Rural Development (NABARD) plays a crucial role in providing credit and fostering development in the agricultural and rural sectors.

- Option 3: Agricultural sector

- NABARD primarily focuses on supporting agriculture by providing credit facilities and infrastructure development, improving agricultural productivity.

- It is responsible for planning, policy-making, and operations in the field of credit for agriculture and other economic activities in rural areas.

- Option 1: Combined sector

- This option is vague, and NABARD does not target sectors in a combined form. Its primary role is specific to agriculture and rural development.

- Option 2: Industrial sector

- NABARD is not primarily focused on the industrial sector, which falls under different financial institutions focused on industry support.

- Option 4: Tertiary sector

- While NABARD facilitates rural infrastructure that might indirectly support tertiary activities, its direct credit provision focuses on agriculture.