Science is still ______ of the causes of many kinds of cancer.

A．ignorant

B．unconscious

C．conscious

D．informed

[单选题]Which of the following usually causes a tree to grow unhealthy?A． Giving a tree a special shape and a definite height.B． Removing small side branches and making a tree look less thick.C． Allowing too many branches to grow in the middle.D． Having a tr

[单选题]The pressure ________ causes Americans选择Thepressure________causesAmericanstobeenergetic,butitalsoputsthemunderaconstantemotionalstrain.A．)tocompeteB)competingC)tobecompetedD)havingcompeted

[单选题]One of the most common causes of reduction gear failure is gear wear caused by scoring as a result ofA．surface fatigue of the gearsB．an inadequate lube oil filmC．plastic flow of the gearsD．fretting corrosion from water

[单选题]One of the reasons that causes oil flowed from sludge outlet of a self-cleaning purifier isA．seal water supply be cut offB．make-up water supply be cut offC．oil outlet valve closed or not open sufficientlyD．the flow rate of oil is too much

[主观题]What causes the lube oil pressure of the engine to drop ?

[单选题]What causes diesel fuel to be ignited in the cylinder of an operating diesel engine?（）A . Spark plugB . Heat of compressionC . CarburetorD . Glow ping

[单选题]The most important factor that causes the wear of the engine parts is （）.A . excessive heatB . frictionC . oxidationD . high pressure

[名词解释] Still病

[试题]Scienceandtechnologyhave___inimportantwaystotheimprovementofagriculturalproduction.A)attachedB)assistedC)contributedD)witnessed

[主观题]Scienceandtechnologyhave___inimportantwaystotheimprovementofagriculturalproduction.A)attachedB)assistedC)contributedD)witnessed