______(49)A. Sofar we have not known exactly yet

______(49)

A. Sofar,we have not known exactly yet whether mouth-to-mouth breathing is really useless in CPR.

B. Only ten percent of the victims treated with traditional CPR survived with good brain a-bility.

C. CPR keeps blood and oxygen flowing to the heart and brain.

D. His studies show that many people do not want to perform mouth-to-mouth breathing on a stranger for fear of getting a disease.

E. It said people should increase the number of chest presses from fifteen to thirty for every two breaths given.

F. No mouth-to-mouth rescue breaths were given to them.