The Statement That There Is Some overlap between Stutterers and Nonstutterers

The statement that there is some overlap between stutterers and nonstutterers in the frequency of disfluencies in their speech means that:

A) frequency of disfluencies is not a very good indicator of the presence of stuttering
B) some people who stutter have fewer disfluencies than some normally fluent people
C) all normally fluent people have fewer disfluencies than some people who stutter
D) most people cannot readily be classified as stuttering or normally fluent