Detailed Explanation:

Priority Sector Lending (PSL) mandates banks to allocate 40% of Adjusted Net Bank Credit (ANBC) to designated sectors including agriculture and allied activities, micro and small enterprises, weaker sections (low-income groups, students for education, housing), export credit, renewable energy, and social infrastructure.

All three options – agriculture, micro and small enterprises, and weaker sections – are explicitly covered under the RBI's PSL guidelines, making option 4 the correct answer.