We drop a piece of metal into a jar full of water, the metal will float if it weighs less than______.

A． an equal amount of silver

B． an equal amount of gold

C． all the water in the jar now

D． the water that leaves the jar

[单选题]We can see _____ full moon on the evening of August ____ 15th every year.A． the； a B. a；a C. a；the D. the；the

[单选题]We are enclosing a full set of copy documents ______this first consignmentA . referringB . coveringC . regarding toD . as for

[单选题]We give you on the attached sheet full details regarding packing and markin9，which must be strictly__________．A . observedB . abide byC . submittedD . seen

[单选题]We really enjoy ourselves at the party.Thanks again, Mr.and Mrs.Brown.-____

[单选题]The main bearing metal is a lining （）.A . inside the bearingB . outside the bearingC . covering the crankshaftD . none of the above

[单选题]Additives （） protective layers on metal surfaces guarding them against corrosion.A . damageB . formC . dissolveD . contaminate

[名词解释] 分泌片（secretory piece）

[名词解释] 特性曲character piece

[多选题] 通常MMC（metal matrix composite）（）A .采用高熔点、重金属作为基体。B .要比基体金属或合金的塑性与韧性差。C .要比基体金属或合金的工作温度高。D .要比基体金属或合金的弹性模量低。

[单选题]The metal sheet used to imitate thunder must be________．A．tightly fastened on all sidesB．lying flatC．both A and BD．neither A nor B