Large populations of tortoises inhabited the galapagos islands before humans. when humans settled on the islands and introduced goats, the number of tortoises declined. what is most likely the explanation for the decrease in the tortoise population?

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.