Holographic c theorems

I will review the current status of how c-theorems in CFTs arise from the AdS/CFT correspondence. I will argue that the usual approach using the null energy condition is inadequate to cover general cases. I will show how to rewrite a general covariant lagrangian which makes the A-type trace anomaly appearing in Cardy's conjecture manifest. This approach may be useful in future general proofs of the holographic c-theorems in diverse dimensions.