Step 1: Identify the years of the commissions and policy
University Education Commission (b) was in 1948-49.
Secondary Education Commission (c) was in 1952-53.
Indian Education Commission (a) was in 1964-66.
National Education Policy (d) was introduced in 2020.
Step 2: Arrange in chronological order
Based on the years, the order is:
(b) University Education Commission (1948-49),
(c) Secondary Education Commission (1952-53),
(a) Indian Education Commission (1964-66),
(d) National Education Policy (2020).
Conclusion:
Hence, the correct order is b, c, a, d.