单项选择题
A.pack-strap carry
B.two man extremities carry
C.fireman's drag
D.four man log roll
单项选择题 An aircraft has indicated that he wants you to change course and follow him. You cannot comply because of an emergency on board. Which signal should you make?（）
单项选择题 An advantage of a dry chemical over a carbon dioxide fire extinguisher is its（）.
单项选择题 An ABC dry chemical fire extinguisher would be LEAST effective against a fire in（）.