Effector cells
are formed in the red bone marrow.
all of these.
are involved in bringing about the immune response of killing pathogens and infected host cells.
are either B plasma cells or Tc cells.
are lymphocytes.

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.

the answer is c.mitochondria. glad to .

that's all i luck!