Concept:
Chaturdandi Prakashika is an important musicological text of South Indian music tradition.
It is associated with the development of the Melakarta system and swara classification.
Step 1: Check 72 Melakarta.
The concept of 72 Melakarta is associated with Chaturdandi Prakashika.
So, A is correct.
Step 2: Check swara terms.
The terms:
\[
Ra,\ Ri,\ Ru,\ Ga,\ Gi,\ Gu
\]
are connected with swara classification in this context.
So, B is correct.
Step 3: Check Kakli Nishad.
The establishment of Kakli Nishad on third shruti is also related to the theoretical content.
So, C is correct.
Step 4: Check remaining statements.
The mention of 33 Alankaras and description of 122 ragas are not selected as correct contents here.
So, D and E are incorrect.
Step 5: Final conclusion.
The correct statements are:
\[
A,\ B,\ C
\]
Hence:
\[
\boxed{\text{(A) A, B, C only}}
\]