Koos's Study Helped Establish the Premise That _______________ Persons Are

Koos's study helped establish the premise that _______________ persons are less likely than others to recognize various symptoms as requiring medical treatment and that these beliefs contribute to differences in the actual use of services.

A) Lower-class.
B) Middle-class.
C) Upper-class.
D) Middle- and upper-class.
E) Lower- and middle-class.