The following table shows some developments about the protection of environment.
Arrange them appropriately in accordance with the years given in column B.
| A |
B |
| 1. Earth Summit |
a. 1997 |
| 2. Limits to growth |
b. 1987 |
| 3. Brundtland report |
c. 1992 |
| 4. Kyoto protocol |
d. 1960 |
