Which of the following problems may occur when using fuel oil with a high sulphur content?（）

A.increase thermal efficiency
B.cause clogging of the fuel system
C.increase the ability of the engine to start in cold weather
D.produce corrosion in the cylinder and exhaust system at low loads

A.the engine to run after the fuel has been secured
B.the engine to over-speed
C.a fire
D.all of the above