Which fact about the moon, as seen from the earth, is evidence that the amount of time the moon takes to complete one rotation and one revolution are nearly identical? a) we usually see the moon at night. b) we cannot see the moon on some nights. c) we always see the same side of the moon from earth. d) we only see a “full moon” for a day or two per lunar cycle.

In an experiment examining the effects tai chi on arthritis pain, callahan (2010) selected a large sample of individuals with doctor-diagnosed arthritis. half of the participants immediately began a tai chi course and the other half (the control group) waited 8 weeks before beginning. at the end of 8 weeks, the individuals who had experienced tai chi had less arthritis pain that those who had not participated in the course.