SRO vs independent regulator

Question:

The media devotes considerable coverage to a regulatory body that has been given autonomy by the government and is empowered by statute. The regulatory body has recently raised the fees charged to the companies it regulates. The regulatory body in question is most likely to be a(n):

  1. self-regulatory organization.
  2. government agency.
  3. independent regulator.

The answer is independent regulator, but is there a reason it couldnt be a SRO? SROs are also given power by the government and are also independent regulators. They also charge the companies they regulate.

Thanks! That makes sense