Which describes fat? A. a lipid that stores energy
B. a nucleic acid that directs cell function
C. a protein that speeds up a chemical reaction
D. a carbohydrate that produces energy

Chronic obstructive pulmonary disease (copd) makes it difficult for the respiratory system to deliver oxygen to the lungs. the scientist wants to use a computer simulation to model how copd affects heart rate and respiratory rate during exercise. she will compare the results of the simulation to the results she gathered in her previous study. which of the following would be an appropriate dependent variable for the new study?