A scientist uses materials in her lab to cut a DNA sample into fragments.
What process is the scientist using
A. Karyotyping
B. Polymerase chain reaction (PCR)
c. Use of restriction enzymes
D. Gel electrophoresis

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.