If an op-amp were perfect the CMRR would be what?

If an operational amplifier (op-amp) were perfect, the Common Mode Rejection Ratio (CMRR) would be infinite. This is because a perfect op-amp would completely reject any common-mode signals while amplifying differential signals without any error. In reality, op-amps have limitations that result in finite CMRR values, but the ideal scenario assumes perfect behavior.