Concept:
The idea of sustainable development evolved gradually as environmental concerns gained global attention.
While awareness began earlier, the formal concept became prominent later.
Step 1:Evaluate Assertion (A).
The concept of sustainable development gained global recognition in the 1980s, especially after the Brundtland Report (1987).
Hence, Assertion (A) is correct.
Step 2:Evaluate Reason (R).
Environmental awareness started growing in the 1960s in Western countries due to issues like pollution, industrialisation, and ecological damage.
Hence, Reason (R) is also correct.
Step 3:Check explanation.
The rise of environmental awareness in the 1960s laid the foundation for the emergence of sustainable development in the 1980s.
Thus, the reason correctly explains the assertion.
Final Conclusion:
\[
\boxed{(A)\ \text{Both (A) and (R) are true and (R) is the correct explanation of (A).
\]