Which of the following is the best expression of the main idea of this passage（）

A．People in beautiful rooms tend to give higher marks to photos of faces than people in ugly rooms.
B．The color and general appearance of a room have a deeper effect on the behavior of the people in it.
C．The University of Kansas has studied the effects of the color of a room on people’s behavior.
D．Beautifully furnished, light-coloured rooms make people more comfortable than ugly, dark rooms.