Which of the following statements is true?
a. symptoms of infection indicate that the body has been overtaken by invading microorganisms.
b. symptoms of infection indicate that the body is trying to combat invading microorganisms.
c. symptoms of infection indicate that the body has successfully defeated invading microorganisms.
d. symptoms of infection indicate that the body is unprepared to combat invading microorganism

B

Explanation:

Symptoms of infection indicate that the body is trying to combat invading microorganisms. Fever for example is a very common symptom with which the body is defending itself against external organisms. The body uses fever as a great weapon because when the body raises up temperature, many of the organisms causing infectionwill tend to be destroyed. For this reason, fever should not be abolished with medicine. It should be maintained in a point were the foreign organisms are killed and the body is protected.

The symptoms such as head ache, fever, tiredness and several other, should be respected, monitored and if it is the case, treated with medicine in case the "battle" of the invasors against the body are winning the battle.  

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.