1. [单选题]当人体失水达体重的多少时就会出现目眩、头痛、呼吸困难等症状：
A. 6%～10%
B. 11%～12%
C. 15%～20%
D. 20%以上
2. [单选题]Exhaust gas pyrometers are useful for
A. detecting faulty combustion in individual cylinders
B. adjusting fuel racks to maintain equal loading between cylinders
C. adjusting the load limit setting of the governor at idle conditions
D. calculating engine horsepower
3. [单选题]磁罗经自差主要随()改变而变化？
A. 航区
B. 时间
C. 航向
D. 舷角
