用电钻钻孔时，不宜用力过大，以免使电钻电动机过载。在钻金属时，注意即将钻通时要减轻用力，以免钻头卡死或伤手。
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简要说明山地丘陵区自然条件的特点。山地的水土保持措施有哪些？
当飞行机组配备3名驾驶员，其中包含一名第二机长时，公司可计划排班的最大飞行时间为多久？
Fire protection regulations for towing vessels require all crew members to know how to perform each of these tasks EXCEPT（）.
A. start the mechanical ventilation system for the engine room
B. operate the fuel shut-off for the engine room
C. operate all fire extinguishing equipment aboard the vessel on board the vessel，including starting the fire pump
D. All of the above
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