Non-gaseous substances which（）naturally as pure elements, such as gold, are rare and are often highly valued.

Diamonds are the hardest substance _______ in nature。

A. find

B. found

C. finding

D. to find

A.Toxic and infectious substance

B.Corrosives

C.Explosives

D.Radioactive Material

A.content

B.body .

C.substance

D.weightiness

A.面临资源短缺的物质 The substance facing a resource shortage###SXB###B.使用强度可能加大的物质 The substance with an increasing uses###SXB###C.其循环流动与其他物质密切相关的物质 The substance whose circulation is closely related to other substances###SXB###D.以上三项都不是 None of the above

The chemical substance missing from polished rice______

A．was vitamin B

B．did not affect the chickens

C．was named the Eijkman vitamin

D．has never been accurately identified

The passage implies that cellulose is a very porous substance because it contains______.

A．a substance that creates pressure

B．millions of tiny holes

C．a substance that dissolves it

D．liquid medicine

A.excited

B.produced

C.created

D.chosen

Spontaneous combustion is caused by ______．

A.An outside heat source heating a substance until it ignites

B.Conduction of heat through a wall of material to the substance

C.Chemical action within a substance

D.All of the above

A.分子

B.粒子

C.物质

D.材料

英译中

Dependence is marked first by an increased tolerance, with more and more of the substance required to produce the desired effect, and then by the appearance of unpleasant withdrawal symptoms when the substance is discontinued.