问题 选择题

下列关于物质的用途叙述不正确的是

A.过氧化钠可用作供氧剂

B.高纯硅用来制造光导纤维

C.镁铝合金可用作制造飞机的材料

D.Cl2可与石灰乳反应制取漂白粉

答案

答案:B

题目分析:A、过氧化钠能与二氧化碳和水反应生成氧气,可用作供氧剂,错误;B、用来制造光导纤维的是二氧化硅,错误;C、镁铝合金强度高、密度较小,可用作制造飞机的材料,正确;D、Cl2可与石灰乳反应生成氯化钙和次氯酸钙,用来制取漂白粉,正确。

选择题
阅读理解

(二)   66  Scientists and experts have proved the uniqueness of finger-prints and discovered that no exactly similar pattern is passed on from parents to children, though nobody knows why this is the case.

The ridge (隆起) structure on a person's fingers does not change with growth and is not affected by surface injuries. Burns, cuts and other damage to the outer part of the skin will be replaced in time by new one, which bears a reproduction of the original pattern.  67   Some criminals make use of this fact to remove their own finger-prints but this is a dangerous and rare step to take.

Finger-prints can be made very easily with printer's ink. They can by be recorded easily.  68  Because of the simplicity and economy of this system, finger-prints have often been used as a method of solving criminal case. A suspected man may deny a charge but this may be in vain. 69  . When a suspect leaves finger-prints behind at the scene of a crime, they are difficult to detect with the naked eye.   70  Some of the marks found are incomplete but identification is possible if a print of a quarter of an inch square can be obtained.

A.Special techniques are used to "develop" them.

B.A fingerprint is an impression of the friction ridges of all part of the finger.

C.It is only when the inner skin is injured that the arrangement will be destroyed.

D.With special methods, identification can be achieved successfully within a short time.E. A latent print is the chance reproduction of the friction ridges deposited on the surface of an item.

F. His finger-prints can prove who he is even if his appearance has been changed by age or accident.

G. Every human being has a unique arrangement of the skin on his fingers and this arrangement is unchangeable.