Joy and sadness are experienced by people in all cultures around the world, but how can we tell when other people are happy or despondent? It turns out that the expression of many emotions may be universal. Smiling is apparently a universal sign of friendliness and approval. Baring the teeth in a hostile way, as noted by Charles Darwin in the nineteenth century, may be a universal sign of anger. As the originator of the theory of evolution, Darwin believed that the universal recognition of facial expressions would have survival value. For example, facial expressions could signal the approach of enemies (or friends) in the absence of language.
The author mentions "Baring the teeth in a hostile way" in order to
A. Differentiate one possible meaning of a particular facial expression from other meanings of it
B. Support Darwin's theory of evolution
C. Provide an example of a facial expression whose meaning is widely understood
D. Contrast a facial expression that is easily understood with other facial expressions
