裸露山体缺口以形成原因分为哪几类？

把下列各段按正确的顺序排列，第一段已给出。

     A. So they went to the great man. The father asked the great man to help him. But the great man liked

sweets himself. He told the father to bring his son back after a month. 

     B. During the month, the great man tried to give up eating sweets. At last he did it. When the boy and his

father returned after a month, the great man had a talk with the boy. From then on the boy did not ask for

sweets any more.

     C. The boy's father thought hard about how to stop the child from asking for so many sweets. A great man

lived nearby. The boy's father decided to take the boy to him. He might be able to make the child give up sweets.

     D. A person's example is always stronger than words. We should not ask others to do what we can't do

ourselves.

     E. The boy's father felt surprised, "Why didn't you ask my son to give up sweets when we came to you a

month ago?" The man answered, "How could I ask a boy to give up sweets when I loved sweets myself? In the

last month I gave up eating sweets." 

     F. Once there was a boy. He loved sweets very much. He always asked his father for sweets.

正确答案：第一段为 F  1. ________   2. ________   3. _______   4. ________    5. _______

对心律失常的诊断哪一项最有价值（）

A.超声心动图

B.心向量图

C.心电图

D.房室束电图

E.心音图

国际上铜的期货交易主要集中于（）。

A.美国

B.日本

C.中国

D.英国

以下哪种心律失常使用非同步电除颤（）。

A.心房颤动

B.心房扑动

C.阵发性室上性心动过速

D.心室颤动

E.室性期前收缩

2008年5月12日，四川汶川发生8.0级地震救援队员利用各种器材展开抢险救灾工作

（1）利用如图所示的钢丝钳，救援队员把钢筋剪断，钢丝钳是______（省力/费力）杠杆使用这种杠杆的缺点是______．

（2）使用撬棒，救援队员把滚落在公路上的石块撬起，如图所示，若救援队员在撬棒D点沿DM方向用力撬起石块1，撬棒的支点是______点；若救援队员在撬棒D点沿DN方向用力撬起石块1，撬棒的支点是______点．