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When an electric current flows through a wire, a magnetic field appears around the wire.
A．travels
B．vibrates
C．alternates
D．fluctuates
答案
更多“When an electric current flows through a wire, a magnetic field appears around the wire.A．”相关的问题
第1题
A．Y
B．N
C．NG
第2题
Compensatory Finance Facility can be used ______.
A．to provide a member nation with its currency.
B．to help a member nation devalue its currency.
C．to help a member nation examine its difficulties.
D．to help a member nation with foreign exchange when it is in difficulty.
第3题
Gas lamps became obsolete when electric lighting became possible．
A．useless
B．fashionable
C．outdated
D．unpopular
第4题
As you sleep, the headband
A．analyses your sleep cycle every 90 minutes.
B．records the time when you fall into deep sleep.
C．communicates wirelessly with a computer.
D．measures the electric activity of your brain.
第5题
When the author said "he was lucky", it means the following except ______.
A．the topic he found in a book a century ago is so strange
B．he often finds that the past has valuable lessons for the future
C．there are many books on electric vehicles in the 20th century
D．books published before 1923 are in the public domain
第6题
As you sleep, the headband
A．analyses your sleep cycle every 90 minutes.
B．records the time when you fall into deep sleep.
C．communicates wirelessly with a computer.
D．measures the electric activity of your brain.
第7题
As you sleep, the headband
A．analyses your sleep cycle every 90 minutes.
B．records the time when you fall into deep sleep.
C．communicates wirelessly with a computer.
D．measures the electric activity of your brain.
第8题
听力原文： The United States is full of automobiles. There are still many families without cars, blt some families have two or even more. However, cats are used for more than pleasure. They are a necessary part of life.
Cars are used for business. They are driven to offices and factories by workers who have no other way to get to their jobs. When salesmen are sent to different parts of the city, they have to drive in order to carry their products. Farmers have to drive into the city in order to get supplies.
Sometimes small children must be driven to school. In some cities school buses are used only when children live more than a mile from the school. When the children are too young to walk that far, their mothers take turns driving them to school. One mother drives on Mondays, taking her own children and her neighbors' children as well. Another mother drives on Tuesdays, another on Wednesdays, and so on. This is called "forming a car pool". Men also form. car pools, with three or four men taking turns driving to the place where they all work. More cur pools should be formed in order to put fewer automobiles on the road and to use less gasoline. Parking is a great problem, and so is the traffic in and around cities. Too many cars are being driven. Something will have to be done about the use of cars.
(23)
A．To get supplies.
B．To get to their jobs.
C．To carry their products.
D．To enjoy themselves.
第9题
What is greenhouse effect？
A．It is produced by the interaction of sunlight and hydrocarbons.
B．It is created when emissions from coal-burning factories and electric utility plants react with air.
C．It is the gradual rise in temperature of the earth atmosphere which is caused by an increase of gases in the air trapping the heat of the sun.
D．It is produced by airborne toxins that are emitted during some manufacturing processes.
