According to Ekman's Research on Facial Expressions

According to Ekman's research on facial expressions:

A) when people try to hide their feelings with an inauthentic expression, they use different groups of muscles than they do for authentic emotions.
B) authentic smiles last ten seconds or more, whereas false smiles last only about two seconds.
C) when trying to feign sadness, only about 60 percent of people manage to get the eyebrows, eyelids, and forehead wrinkle exactly right.
D) there is little support for Darwin's evolutionary theory that certain human facial expressions are innate.