At the University of Kansas art museum, scientists tested the effect of different colored walls on two groups of visitors to an exhibit of paintings.
For the first group the room was painted white; for the second, dark brown. Movement of each group was followed by an electrical equipment under the carpet.
The experiment showed that those who entered the dark brown walked more quickly, covered more area, and spent less time in the room than people in the white one. Dark brown made people more active, but the activity ended sooner.
Not only the choice of colors but also the general appearance of a room affects those inside. Another experiment presented people with photographs of faces whose energy was to be commented. Three groups of people were used; each was shown the same photos, but each group was in an ordinary room--a nice office. The third was in a tastefully designed living room with carpeting.
Results showed that the people in the beautiful room tend to give higher marks to the faces than those in the ugly room did. Other studies that students do better on tests taken in comfortable room than in ordinary-looking or ugly rooms.
What is referred to as the “general appearance” in this passage is ____.（ ）
参考文章后半部分，可知A选项文中未提及，B，C三项只回答了一部分，D选项最准确。
