题目

对于如图所示的电路，下列说法正确的是（    ）A．a、b端接稳恒直流电，灯泡发亮B．a、b端接交变电流，灯泡发亮C．a、b端接交变电流，灯泡发亮，且将电容器电容增大时，灯泡亮度减小D．a、b端接交变电流，灯泡发亮，且将电容器电容减小时，灯泡亮度不变  答案：B解析:电容器的作用是“隔直流，通交流”“阻低频，通高频”，电容器的阻碍作用会随着交变电流的频率的增大而减小，电容器的电容越大，阻碍作用越小，可知B对； Season There are only two seasons in some countries—the dry season and the rainy season. They are India,Vietnam and some countries in Africa. It’s never cold there and it doesn’ t snow. In the dry season it is as warm as it is in the rainy season. When it is the dry season,itdoesn’t rain at all. It ’s very,very hot. All grass and leaves in thetrees are yellow. Animals and people are very thirsty. It is a very difficult time for them!When it is the rainy season,the rain doesn’t stop,it rains day and night. There is a lot of water around!Some animals like it,but some don’t. There is a place where there are no seasons at all. It is the Antarctic (南极). It is very cold all the year round. There are no countries and no cities there. There are some villages in the Antarctic. Who lives there? Some scientists from some countries go there to learn about the coldest place,its animals and birds. But there are no trees,no flowers,no fruit there,so people can’t live there long.() 1. There are seasons in the Antarctic.   A. two   B. three   C. four  D no() 2. What* s the weather like in Vietnam?   A. It’s very cold all the year round.   B. It’s never cold and it doesn’t snow.   C. It is very cold and it snows all the year round.   D. It is never cold and it snows all the year round.() 3. When is a difficult time for people and animals in India?   A. The rainy season. B. Spring. C. The dry season. D. Winter.() 4. Some scientists live in the Antarctic because they want to learn about .   A. the coldest place   B. the countries there   C. the cities   D. the fruit there() 5. Which of the following sentences is NOT true in the passage?   A. The leaves on the trees are yellow in the dry season.   B. All countries in Africa have two seasons.   C. Some animals like the rainy season.   D. There are some animals and birds in the Antarctic.