Which of the following precautions must be taken if an electric immersion heater is used to keep the coolant in a diesel engine warm during the time the engine is secured?（）

Sea water is not directly used as a coolant for engines because of its （）.

Sea water is not directly used as a coolant for engines because of its （）.

If the coolant temperature of a closed cooling water system for a diesel engine gradually increases, the trouble usually is （）

Engine coolant accumulating in the diesel engine lubricating oil can result from a （）

Which of the following precautions must be taken if an electric immersion heater is used to keep the coolant in a diesel engine warm during the time the engine is secured?（）

If the coolant temperature of a closed cooling water system for a diesel engine gradually increases, the trouble usually is （）

Sea water is not used directly as a coolant because of （）.

Sea water is not used directly as a coolant because of （）.

Engine coolant accumulating in the diesel engine lubricating oil can result from a （）