Empyema is defined as an

Choice A reason: Infection in the blood is not empyema. It is sepsis, which is a life-threatening condition that occurs when the body's response to infection causes tissue damage, organ failure, or death.

Choice B reason: Infection in the pleural space is empyema. It is a collection of pus in the space between the lungs and the chest wall, usually caused by a bacterial infection that spreads from the lungs or the chest cavity.

Choice C reason: Exudative bronchitis is not empyema. It is a type of bronchitis that involves inflammation and excess mucus production in the bronchi, the airways that carry air to the lungs.

Choice D reason: Infection localized in the lung is not empyema. It is pneumonia, which is an inflammation of the lung tissue, usually caused by a viral or bacterial infection that affects the air sacs or the interstitial tissue.

Choice A reason: This is not the definition of ejection fraction. The percentage of blood that leaves the heart in a minute is related to the cardiac output, which is the product of the heart rate and the stroke volume.

Choice B reason: This is the correct definition of ejection fraction. It is the ratio of the stroke volume (the amount of blood pumped by the left ventricle) to the end-diastolic volume (the amount of blood in the left ventricle at the end of diastole). It is a measure of the efficiency of the heart and reflects the contractility of the cardiac muscle.

Choice C reason: This is not the definition of ejection fraction. The amount of blood that leaves the heart with each beat is the stroke volume, which is one of the factors that determine the ejection fraction.

Choice D reason: This is not the definition of ejection fraction. The amount of blood that leaves the heart in a minute is the cardiac output, which is influenced by the ejection fraction, but not equivalent to it.