Concept:
In Hindu iconography, different forms represent different religious ideas and stories.
Kalyan Sundaram and Ardhanarishwar are two different forms related to Shiva and Parvati.
Step 1: Check Assertion (A).
Kalyan Sundaram represents the marriage of Shiva and Parvati.
So, Assertion (A) is correct.
Step 2: Check Reason (R).
Ardhanarishwar represents Shiva and Shakti in one combined form.
In this form, one half is Shiva and the other half is Parvati or Shakti.
So, Reason (R) is also correct.
Step 3: Check whether Reason explains Assertion.
Although both statements are correct, Ardhanarishwar does not explain Kalyan Sundaram.
Kalyan Sundaram is about the marriage of Shiva and Parvati.
Ardhanarishwar is about the unity of Shiva and Shakti in one body.
Therefore, Reason is not the correct explanation of Assertion.
Step 4: Final conclusion.
Both Assertion and Reason are correct, but Reason does not explain Assertion.
Hence:
\[
\boxed{\text{(B)}}
\]