Patients with Chronic Obstruction Pulmonary Disease (COPD) Volunteered to Be

Patients with chronic obstruction pulmonary disease (COPD) volunteered to be tested for exhaled nitric oxide (eNO) while resting and after a 6 minute walk test. Each subject was measured under each condition, and the order of presentation (resting then walking or the other way around) was randomized. Researchers believe the eNO should be higher while walking than resting for COPD patients. Which best describes this study design?

A) Paired using repeated measures
B) Paired using matching
C) Independent groups