Final answer:
The lurking variable in this experiment is the emotional state of the residents. The explanatory variable is herbal tea. The conclusion from this study is that there is some evidence that herbal tea may improve one's emotional state.
Step-by-step explanation:
1. The lurking variable in this experiment is d. the emotional state of the residents. Lurking variables are those that are not intentionally measured or controlled in an experiment but can still influence the results. In this case, the emotional state of the residents could have an impact on their cheerfulness and overall health, independent of the herbal tea or visits of the college students.
2. The explanatory variable in this experiment is b. herbal tea. The explanatory variable is the one that the researchers manipulate or provide in order to see its effect on the response variable. Here, the college students are serving herbal tea to the residents, and the researchers are interested in seeing if the herbal tea has a restorative effect on their cheerfulness and health.
3. The correct conclusion from this study is c. There is some evidence that herbal tea may improve one's emotional state. The results would be completely convincing if a scientist had conducted the study rather than a group of college students. While the study conducted by the college students provides some evidence that herbal tea may have restorative powers, it would be more convincing if a scientist had conducted the study using more controlled conditions and a larger sample size.