9. an head shake is a(n) non-manual marker, while a head nod is a(n) non-manual marker. a. affirmative, negative b. negative, affirmative c. sad, happy d. happy, sad

b. negative, affirmative

Explanation:

In the western cultura a head shake can mean a negative marker while a nod can be used intentionally as an affirmative.  But it is true that everything is linked to the evolutionary processes of each species, which determine the types of behavior and gestures. Even animals develop and use codes to express themselves. Allied to this, there are cultural factors that end up differentiating or reversing these movements. From when we were born, we learned these gestures by watching our parents and others.

answer; ( action training environment;

answer; the changing age structure of the population;