什么是需要需要分为哪些种类

男性，34岁，3小时前突然出现腹部刀割样疼痛，迅速波及全腹；查腹部板样硬，压痛明显，伴反跳痛，肝浊音界消失，肠鸣音消失。

对患者诊断最有帮助的辅助检查为（）

A.腹部CT

B.腹部B超

C.腹部立位X线

D.胸部X线平片

E.心电图

进口货物收货人在有关货物进境后海关放行前，可以向海关申请不提取货物而将货物直接退运境外。下列属于可以办理直接退运范围的是( )。

A．收货人因故未能支付进口各项税费的

B．经海关审核、检验，发现有走私嫌疑的

C．属错发、误卸货物，能提供承运部门书面证明的

D．合同执行期间国家贸易管制政策调整，收货人无法补办有关审批手续，并能提供有关证明的

何为发动机拉缸及其原因、损坏有哪些？

Vitamins are organic compounds necessary in small amounts in the diet for the normal growth and maintenance of life of animals, including man.

They do not provide energy, 21 do they construct or build any part of the body. They are needed for 22 foods into energy and body maintenance. There are thirteen or more of them, and if 23 is missing a deficiency disease becomes 24 .

Vitamins are, similar because they are made of the same elements--usually carbon, hydrogen, oxygen, and 25 nitrogen. They are different 26 their elements are arranged differently, and each vitamin 27 one or more specific functions in the body.

28 enough vitamins is essential to life, although the body has no nutritional use for 29 vitamins. Many people, 30 , believe in being on the "safe side" and thus take extra vitamins. However, a well-balanced diet will usually meet all the body’s vitamin needs.

30（）

A．nevertheless

B．therefore

C．moreover

D．meanwhile

启动印刷机前，必须先按动开机（），打出开机信号后才能启动印刷机。

A.电铃

B.喇叭

C.灯光

D.电源