i think that the answer is c, but i just want to make sure. any would be appreciated.
which of the following is one way that soil can be managed properly?
a. over-irrigate crops.
b. remove all the topsoil from the area.
c. rotate the crops.
d. plant the same crop in the same field, year after year.

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.