Which of the following is transparent

A:Aluminium. B:Silver. C:Milk. D:Mineral water.

Passage Two Look at a man walking down a street or road in’ the sunlight and you will see his shadow. If you watch two men walking in the sunlight and carrying a six-fool pane(窗玻璃片) of glass between them, you will see each man six feet apart, but there will be no shadow of the pane of glass. Shadows are easily explained since we know that light travels in a straight line. We also know that light waves pass through some bodies and not through others. When light strikes a body and passes through it unchanged, we call such a body or material transparent. Most glass is such a material, especially window glass, and it is for this reason that we do not see the shadow of the window pane which the men are carrying. Do you know of any other transparent materials The most common one, with which we are familiar, is air. Another is clear water. On the other hand, some materials do not let light pass through them at all. They stop the light waves just as you would-catch a ball that was being thrown to someone standing between you. Such materials are called opaque. Men’ s bodies, like steel, rock, concrete or even cardboard, are opaque and do not permit the light to pass through. An opaque body casts a shadow.

A:Light waves are beams of light. B:Light waves can penetrate any materials except men' s bodies. C:Light waves can penetrate transparent materials. D:Light waves can penetrate some materials.

Passage Two Look at a man walking down a street or road in’ the sunlight and you will see his shadow. If you watch two men walking in the sunlight and carrying a six-fool pane(窗玻璃片) of glass between them, you will see each man six feet apart, but there will be no shadow of the pane of glass. Shadows are easily explained since we know that light travels in a straight line. We also know that light waves pass through some bodies and not through others. When light strikes a body and passes through it unchanged, we call such a body or material transparent. Most glass is such a material, especially window glass, and it is for this reason that we do not see the shadow of the window pane which the men are carrying. Do you know of any other transparent materials The most common one, with which we are familiar, is air. Another is clear water. On the other hand, some materials do not let light pass through them at all. They stop the light waves just as you would-catch a ball that was being thrown to someone standing between you. Such materials are called opaque. Men’ s bodies, like steel, rock, concrete or even cardboard, are opaque and do not permit the light to pass through. An opaque body casts a shadow.

A:"Why are there shadows" B:"The transparent materials" C:"How to cast a shadow" D:"Shadows and light waves"

英译汉：“packing material；flexible package；transparent package”（）

A:包装材料；固定包装；透明包装 B:包装袋；灵活包装；透明包装 C:软包装；透明包装；包装材料 D:包装材料；软包装；透明包装

VLAN中继协议(VTP)用于在大型交换网络中简化VLAN的管理。按照VTP协议，交换机的运行模式分为3种：VTP Server、VTP Client和VTP Transparent。下面关于VTP的协议描述中，错误的是 (28) 。

A:交换机在VTP Server模式下能创建、添加、删除和修改VLAN配置 B:一个VTP管理域中只能设置1个VTP Server C:在VTP Transparent模式下可以进行VLAN配置，但不能向其他交换机传播配置信息 D:交换机在VTP Client模式下不允许创建、修改或删除VLAN

虚拟局域网中继协议(VTP)有3种工作模式，即VTP Server、VTP Client和VTP Transparent。以下关于这3种工作模式的叙述中，不正确的是（）。

A:VTP Server可以建立、删除和修改VLAN B:VTP Client不能建立、删除或修改VLAN C:VTP Transparent不从VTP Server学习VLAN的配置信息 D:VTP Transparent不可以设置VLAN信息

虚拟局域网中继协议(VTP)有三种工作模式，即VTP Server、VTP Client和VTP Transparent。以下关于这三种工作模式的叙述中，不正确的是______。

A:VTP Server可以建立、删除和修改VLAN B:VTP Client不能建立、删除或修改VLAN C:VTP Transparent不从VTP Server学习VLAN的配置信息 D:VTP Transparent不可以设置VLAN信息