To test how fertilizer affects tomato plants, a farmer divided a field of young tomato plants into 10 plots of equal size. the farmer then put fertilizer on half of the plots and no fertilizer on the other half of the plots. what is the control group in this experiment?

a. all the weedy plants in all the plots
b. the tomato plants in all the unfertilized plots
c. the tomato plants in all the fertilized plots
d. all the tomato plants in the field

the oxygenated blood then leaves the lungs through pulmonary veins, which return it to the left heart, completing the pulmonary cycle. this blood then enters the left atrium, which pumps it through the mitral valve into the left ventricle. from the left ventricle, the blood passes through the aortic valve to the aorta.

deoxygenated blood leaves through the right ventricle through the pulmonary artery. from the right atrium, the blood is pumped through the tricuspid valve (or right atrioventricular valve), into the right ventricle.