When Using a Functional Outcome for a Patient Receiving Medicare

When using a functional outcome for a patient receiving Medicare coverage, which impairment, limitation, or restriction is identified with the modifier "CK"?

A) At least 1% but less than 20% impaired, limited or restricted
B) At least 20% but less than 40% impaired, limited or restricted
C) At least 40% but less than 60% impaired, limited or restricted
D) At least 60% but less than 80% impaired, limited or restricted