A、They will make visitors walk slower. B、They will make visitors stay in the room for a longer time. C、They will stimulate more

Investigators were testing the effects 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 system under the carpet. The experiment revealed that those who entered the dark brown room walked more quickly, covered more area, and spent less time in the room than the people in the white environment.
(17) Dark brown stimulated more activity, but the activity ended sooner. Another experiment presented three groups of subjects with the same photographs, but each group was in a different kind of room—an “ugly” room like a messy storeroom, an average room, such as a nice office, and a tastefully designed living room with carpeting. (18) Results showed that the subject in the beautiful room tended to give higher ratings to the faces than did those in the ugly room. Other studies suggest that students do better on tests taken in comfortable, attractive rooms than in ordinary-looking or ugly rooms.
Questions 16 to 19 are based on the passage you have just heard.
16. What is the main idea of the passage?
17. How will dark color influence visitors at an exhibition?
18. How will beautiful rooms influence visitors?
19. What can be concluded from the two experiments?