The Earlier Concept of "Masked" Depression Was That

The earlier concept of "masked" depression was that:

A) children wear a characteristic "mask" of depression,including downcast eyes and downturned mouth
B) it is difficult to diagnose depression in children because they "mask" their feelings with a happy face
C) children purposely conceal or "mask" their depression so as to avoid treatment
D) depression could be "masked" or concealed by a variety of other behaviors,and thus any clinical symptom could be evidence of underlying depression