Step 1:
Bhasa composed a famous Sanskrit play named:
\[
\boxed{\text{Dutavakyam}}
\]
Hence, Assertion A is correct.
Step 2:
In the drama, Lord Krishna acts as a messenger (duta/ambassador).
Thus, Reason R is correct.
Step 3:
The title “Dutavakyam” is directly connected with Krishna’s diplomatic mission.
Therefore, R correctly explains A.
Step 4:
Hence:
\[
\boxed{\text{Both A and R are correct and R is the correct explanation of A}}
\]
Thus, the correct answer is:
\[
\boxed{\text{(1)}}
\]