单项选择题
The rescuer can best provide an airtight seal during mouth-to-mouth resuscitation by pinching the victim’s nostrils and（）.
A.cupping a hand around the patient's mouth B.keeping the head elevated C.applying his mouth tightly over the victim's mouth D.holding the jaw down firmly
单项选择题 The principal personnel hazard unique to Halon extinguishers is（）.
单项选择题 The most effective warming treatment for a crew member suffering from hypothermia is（）.
单项选择题 The danger associated with using carbon dioxide in an enclosed space is（）.
