问题 单项选择题

在互联的网络设备中,交换机的工作与网桥相比,区别在于 (26) ,网桥是根据 (27) 知道它是应该转发还是应该过滤掉数据包的。交换机与HUB相比,优点是 (28) 。网桥中为了防止产生循环路径,需要运行 (29) 算法。具有自学习功能的网桥是 (30)

A.IP

B.Trunking

C.生成树

D.PPP

答案

参考答案:C

解析: 生成树算法。

单项选择题

The blue of the sea is caused by the scattering of sunlight by tiny particles suspended in the water. Blue light, being of short wavelength, is scattered more efficiently than light of longer wavelengths. Although waters of the open ocean are commonly some shade of blue, green water is commonly seen near coasts, especially in tropical or subtropical regions. This is caused by yellow pigments being mixed with blue water. Phytoplankton are one source of the yellow pigment. Other microscopic plants may color the water brown or brownish-red. Near the shore, silt or sediment in suspension can give water a brownish hue. Outflow of large rivers can often be observed many miles offshore by the coloration of suspended soil particles.Marine phytoplankton (Greek for "plant wanderers") are microscopic single-celled plants that include diatoms, dinoflagellates, coccolithophorids, green algae, and blue-green algae, among others. The growth of these organisms, which photosynthesize light, depends on a delicate balance of nutrient enrichment via vertical mixing, which is often limited by the availability of nitrogen and light. Diatoms are one-celled plants with patterned glass coverings. Each glass, or silicon dioxide box, is ornamented with species-specific designs, pits, and perforations making them popular with microscopists and, more recently, electron scanning microscopists.

The main idea of this passage is that________.

A.light causes sea color

B.sea coloration is varied because of a combination of length of light waves and microscopic plant life and silt

C.microscopic plant life causes sea color

D.water composition causes sea color

单项选择题