Manufacturers found out that color affects sales _

单项选择题

The fact that blind people can "see" things using other parts of their bodies apart from their eyes may help us to understand our feelings about color. If they can sense color differences then perhaps we, too, are affected by color unconsciously.
Manufacturers have discovered by trial and error that sugar sells badly in green wrappings, that blue foods are considered unpleasant, and the cosmetics (化妆品) should never be packaged in brown. These discoveries have grown into a whole discipline of color psychology that now finds application in oeverything from fashion to interior decoration. Some of our preferences are clearly psychological. Dark blue is the color of the night sky and therefore associated with passivity and calm, while yellow is a day color with associations of energy and incentive. For primitive man, activity during the day meant hunting and attacking, while he soon saw as red, the color of blood and rage and the heat that came with effort. And green is associated with passive defense and self-preservation.
Experiments have shown that colors, partly because of their physiological associations, also have a direct psychological effect. People exposed to bright red show an increase in heartbeat, and blood pressure; red is exciting. Similar exposure to pure blue has exactly the opposite effect; it is a calming color. Because of its exciting connotation(涵义), red was chosen as the signal for danger. But closer analysis shows that a vivid yellow can produce a more basic state of alertness and alarm, so fire engines and ambulances in some advanced communities are now rushing around in bright yellow colors that stop the traffic dead.

Manufacturers found out that color affects sales ______.

A．by experience over a long period of time
B．by experimenting with different colors
C．by trying out color on blind people
D．by developing the discipline of color psychology