Which Best Describes a Minimal Clinically Important Difference (MCID)

Which best describes a minimal clinically important difference (MCID) ?

A) The minimal level of change required in response to an intervention before the outcome would be considered worthwhile in terms of a patient or client's function or quality of life
B) The greatest level of change required in response to an intervention before the outcome would be considered worthwhile in terms of a patient or client's function or quality of life
C) The minimal level of change required in response to an intervention before the outcome would be considered useless in terms of a patient or client's function or quality of life
D) The greatest level of change required in response to an intervention before the outcome would be considered useless in terms of a patient or client's function or quality of life