英语专四相当于什么水平？

Television is a ______ in the transmission of message.

A．sender

B．receiver

C．transmitting device

D．none of the above

During the first half of the seventeenth century, when the nations of Europe were quarreling over who owned the New World, the Dutch and the Swedes founded competing villages ten miles apart on the Delaware River. Not long afterward, the English took over both places and gave them new names, New Castle and Wilmington.

For a century and a half the two villages grew rapidly, but gradually Wilmington gained all the advantages. It was a little closer to Philadelphia, so when new textile mills opened, they opened in Wilmington, not in New Castle. There was plenty of water power from rivers and creeks at Wilmington, so when young Irenee DuPont chose a place for his gunpowder mill, it was Wilmington he chose, not New Castle. Wilmington became a town and then a city —a rather important city, much the largest in Delaware. And New Castle, bypassed by the highways and waterways that made Wilmington prosperous, slept ten miles south on the Delaware River. No two villages with such similar pasts could have gone such separate ways. Today no two pieces could be more different.

Wilmington, with its expressways and parking lots and all its other concrete ribbons and badges, is a tired old veteran of the industrial wars and wears a vacant stare. Block after city block where people used to live and shop is broken and empty.

New Castle never had to make way for progress and therefore never had any reason to tear down its seventeenth-and eighteenth-century houses. So they are still here, standing in tasteful rows under ancient elms around the original town green. New Castle is still an agreeable place to live. The pretty buildings of its quiet past make a serene setting for the lives of 4,800 people. New Castle may be America's loveliest town, but it is not an important town at all. Progress passed it by.

Poor New Castle.

Lucky Wilmington.

Which is the major factor that made the difference between Wilmington and New Castle?

A．Convenience for traffic.

B．The Delaware River.

C．The investment of Irenee DuPont.

D．The textiles mills.

Telecommunications stand for devices and systems that transmit electronic or optical signals across long distances. Telecommunications enables people around the world to contact one another, to access information instantly, and to communicate from remote areas. Telecommunications usually involves a sender of information and one or more recipients linked by a technology, such as a telephone system, that transmits information from one place to another. Telecommunications enables people to sand and receive personal messages across town, between countries, and to and from outer space. It also provides the key medium for delivering news, data, information, and entertainment.

Telecommunications devices convert different types of information, such as sound and video, into electronic or optical signals. Electronic signals typically travel along a medium such as copper wire or are carried over the air as radio waves. Optical signals typically travel along a medium such as strands of glass fibers. When a signal reaches its destination, the device on the receiving end converts the signal back into an understandable message, such as sound over a telephone, moving images on a television, or words and pictures on a computer screen.

Telecommunications messages can be sent in a variety of ways and by a wide range of devices. The messages can be seat from one sender to a single receiver (point-to-point) or from one sender to many receivers (point-to-multipoint). Personal communications, such as a telephone conversation between two people or a facsimile (fax) message (see Facsimile Transmission), usually involve point-to-point transmission. Point-to-multipoint telecommunications, often called broadcasts, provide the basis for commercial radio and television programming.

Telecommunications begin with messages that are converted into electronic or optical signals. Some signals, such as those that carry voice or music, are created in an analog or wave format, but may be converted into a digital or mathematical format for faster and more efficient transmission. The signals are then sent over a medium to a receiver, where they are decoded back into a form. that the person receiving the message can understand. There are a variety of ways to create and decode signals, and many different ways to transmit signals.

Individual people, businesses, and governments use many different types of telecommunications systems. Some systems, such as the telephone system, use a network of cables, wires, and switching stations for point-to-point communication. Other systems, such as radio and television, broadcast radio signals over the air that can be received by anyone who has a device to receive them. Some systems make use of several types of media to complete a transmission. For example, a telephone call may travel by means of copper wire, fiber-optic cable, and radio waves as the call is sent from sender to receiver. All telecommunications systems are constantly evolving as telecommunications technology improves. Many recent improvements, for example, offer high-speed broadband connections that are needed to send multimedia information over the Internet.

Personal computers have pushed the limits of the telephone system as more and more complex computer messages are being sent over telephone lines, and at rapidly increasing speeds. This need for speed has encouraged the development of digital transmission technology. The growing use of personal computers for telecommunications has increased the need for innovations in fiber-optic technology.

Telecommunications and information technologies are merging and converging. This means that many of the devices now associated with only one function may evolve into more versatile equipment. This convergence is already happening in various fields. Some telephones and pagers are able to store not only phone numbers but also names and personal information abo

A．Current development.

B．Transmission of message.

C．Computer networking.

D．Government regulation.