The matching surfaces allow for movement in multiple directions.
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Risk-benefit analysis is the comparison of the risk of a situation to its related benefits.
<span>For research that involves more than minimal risk of harm to the subjects, the investigator must assure that the amount of benefit outweighs the amount of risk. Only if there is the favorable risk-benefit ratio, a study may be considered ethical.</span>
The flu attacks the lungs, nose, and throat. Young children, older adults, pregnant women, and people with chronic disease or weak immune systems are at high risk. a highly contagious viral infection of the respiratory passages causing fever, severe aching, and catarrh, and often occurring in epidemics.