The right answer is B. Begin chest compressions.
Chest compression is a first aid gesture that occurs under two circumstances:
** the victim is conscious and chokes (total obstruction of the upper airways) but can not practice Heimlich's method (example of a pregnant woman or an obese person, or an infant on which the method Mofenson failed, or an unconscious victim for whom the insufflations do not pass); the purpose here is to cause an overpressure in the lungs to dislodge the foreign body;
** the victim is unconscious, does not breathe and his heart is no longer beating, the chest compressions are used here to circulate the blood; alternating thirty chest compressions and two breaths (mouth-to-mouth); all artificial ventilation / cardiac massage is called cardiopulmonary resuscitation (CPR).
One important concept to know that was not mentioned in the question or in the propositions is that there has to be a cardiopulmonary arrest to start the chest compression because there is we may have an unconscious victim who does not respond but breathes!