When a foreign particle gets stuck in the wind pipe that leads to obstruction of flow of air results in choking. The reliable method prepared her for helping with Lena's injury is a training session on CPR i.e., option B.
It is Cardiopulmonary resuscitation which is a life-saving technique used in several emergency situations like choking, heart attack, etc.
CPR starts with 30 chest compressions followed by two rescue breaths.
Thus, the correct option is B.
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