We can infer from the passage that the water table lies .A. between the topsoil layer and the subsoil layerB. in the subsoil layer above bedrockC. between the subsoil layer and bedrockD. in the bedrock layer beneath the subsoil

● TCP/IP communication protocol contains four layers. From bottom to top, the four layers are __(71)__.

（71）A．network interface layer, internet layer, transport layer and application layer

B．internet layer, network interface layer, transport layer and application layer

C．network interface layer, transport layer, network interface layer and application layer

D．application layer, transport layer, internet layer and network interface layer

A. Application Layer

B. Presentation Layer

C. Data Link Layer

D. Physical Layer

A. OSPF is not supported by the design

B. HSRP is not supported by the design

C. preempt tuning of the default gateway is needed

D. the design implements Layer 3 between the access switch and the distribution switch

A. use a Layer 2 link between distribution switches

B. use a Layer 3 link between distribution switches

C. use a redundant link to the core

D. use a Layer 3 link between distribution switches with route summarization

● Networks can be interconnected by different devices. In the physical layer，networks can be connected by（1）or hubs，which just move the bits from one network to an identical network. One layer up we find bridges and switches，which operate at data link layer. They can accept（2）,examine the MAC address，and forward the frames to a different network while doing minor protocol translation in the process. In the network layer，we have routers that can connect two networks. If two networks have（3）network layer， the router may be able to translate between the packet formats. In the transport layer we find transport gateway， which can interface between two transport connections. Finally，in the application layer， application gateways translate message（4）.As an example， gateways between Internet e-mail and X.400 e-mail must （5）the e-mail message and change various header fields.

（1）

A.reapers

B.relays

C.connectors

D.modems

（2）

A.frames

B.packets

C.packages

D.cells

（3）

A.specia l

B.dependent

C.similar

D.dissimilar

（4）

A.syntax

B.semantics

C.language

D.format

（5）

A.analyze

B.parse

C.delete

D.create

______ means the seabed and ocean floor and subsoil thereof，beyond the limits of national jurisdiction．

A.AREA

B.PLACE

C.SEA ROOM

D.WATER

A. Application Layer

B. Transport Layer

C. Internet Layer

D. Network Access Layer

A. Server-to-server traffic always remains in the core layer.

B. The recommended practice is for the core infrastructure to be in Layer 3.

C. The boundary between Layer 2 and Layer 3 should be implemented in the aggregation layer.

D. The Cisco Express Forwarding hashing algorithm is the default, based on the IP address and Layer 4 port.

E. Core layer should run BGP along with an IGP becauseiBGP has a lower administrative distance than any IGP.

Cisco IDS sensors form the eyes and ears of your Cisco network intrusion detection system.Placing sensors correctly throughout your network is crucial to successfully implementing your Cisco intrusion detection system . Where can an IPS sensor be placed in an enterprise network?（）

A. core layer

B. bridging two VLANs on one switch

C. between two Layer 2 devices withtrunking

D. between two Layer 2 devices withouttrunking

D

Have you ever noticed the colour of the water in a river or stream after a heavy rainfall? What do you think caused this change in colour? It is soil that has been washed into the river from the riverbank or from t}le nearby fields.

Components of Soil

Soil is made up of a number of layers（层），each having its own distinctive colour and texture. The upper layer is known as the litter. It acts like a blanket. limiting temperature changes and reducing water loss. The topsoil layer is made up of small particles of rock mixed with rotten plant and animal matter called humus（腐殖质），which is black and gives the topsoil its dark colour. This layer is usually rich in nutrients，oxygen，and water. Below the topsoil is the subsoil，a layer that contains more stones mixed with only small amounts of organic matter. This layer is lighter in colour because of the lack of humus. Beneath the soil lies a layer of bedrock.

Soil forms from the bottom up. Over time bedrock is attacked by rain, wind，frost, and snow. It is gradually broken down into smaller particles in a process called weathering. Plants begin to grow，and rotten materials enrich the topsoil. Most of the soil in Eastern Canada. for example. Was formed from weathered rock that was exposed when the ice disappeared l2,000 years ago.

Water Beneath the Soil

Surface water collects and flows above the ground in lakes. ponds. and rivers. Once in the soil or rock，it is called groundwater. Gravity pulls groundwater through the soil in a process called percolation（渗透）. Eventually the water reaches a layer called the water table. Under this is bedrock through which water cannot percolate.

As water percolates downward，it dissolves organic matter and minerals from the soil and carries them to deeper layers. This causes a serious problem because plants require these nutrients for growth.

Soil pH

Soil can be acidic. neutral. or basic. The pH of the soil is determined by the nature of the rock

from which it was formed. and by the nature of the plants that grow and rot in it.

The acidity of rain and snow can lower the pH of the groundwater that enters the soil. By burning fossil fuels such as coal，oil and gasoline，humans have been contributing to higher levels of acidity in many soils. When fossil fuels are burned. gases are released into the air and then fall back to earth as acid rain. Acid soil increases出e problem of carrying nutrients to lower soil levels. As nutrients are removed，soil is less fertile. Plants grow more slowly in acidic soil，and also become easily attacked by diseases.

67. The layer of soil that provides necessary nutrients for plant growth is called.

A. 1itter B. topsoil C. humus D. subsoil

根据下面的文字资料回答 71～75 题 connected by（ 1 ）or Hubs,which just move the bits from one network to an identical network. One layer up we find bridgas and swiehes,which operate at data link layer. They can accept （ 2 ） , examine the MAC address, and forward the frames to a different network while doing minor protocol translation in the process. In the network layer,we have touters that can connect two netwoks. If two networks have（ 3 ）network layer,the router may be able to translate between the packet formats. In the transport layer we find transport gateway, which cart interface between the two transport connections. Finally, in the application layer, application gateways translate message（ 4 ）. As an example,gateways between Internet e-mail and X.400 e-mail must （ 5 ）the e-mail message and change various header fields.

第6题：文中（ 1 ）处正确的答案是（ ）。

A．reapers

B．relays

C．connects

D．modems