Which of the following behaviors allows a bird to maintain a constant body temperature in extremely hot weather?
a. spreading wings
c. flattening feathers
b. panting
d. all of the above
user: bird bones are adapted for flight because they
a. are dense
c. are hollow
b. contain bone marrow
d. are longer than the bones of most animals

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.