Explanation:

- Challenge of Rural Credit: Many farmers and rural businesses struggle to access financial services. Limited access to credit hampers agricultural productivity and rural development.

- Challenge of Rural Marketing: Rural areas often face difficulties in marketing their products due to poor infrastructure, lack of market information, and intermediaries who take large cuts.

- Challenge of Unemployment: Rural unemployment remains a significant issue, with limited job opportunities outside agriculture, leading to underemployment and migration to urban areas.

- Both a and b: This option includes both the challenge of rural credit and the challenge of rural marketing. These are interconnected as financing is needed for effective marketing.