题干

利用钨制作灯泡里的灯丝,而不用锡的主要原因是(  )


A:钨有导电性,而锡没有

B:钨很细,而锡很粗

C:钨熔点高,而锡熔点低

D:钨便宜,而锡很贵

上一题 下一题 0.0难度 选择题 更新时间:2015-12-23 06:51:35

答案(点此获取答案解析)

C

同类题3

阅读理解

    One of the hardest parts of living abroad is being away from your loved ones, especially your family. While my friends are so important to me, I've personally found it more difficult being away from family.

    However, I was fortunate that my mum and sister recently found the time to see me. Both my sister and I have major birthdays this year as she's tuming 18 and I'll be 21. My sister is a very big music fan and this year, I created my status as the best older sister by keeping an eye out for music concerts in Paris. In our home town of Leicester, we don't regularly get many well-known artists playing in our city. But in Paris, I managed to get the best 18th birthday present of all: tickets for all three of us to see my sister's favorite American rapper, Angel Haze.

    I will try to visit for my sister's actual birthday in June, the chance for my sister and my mum to visit became a birthday treat. The experience of finding our way together to the concert or getting to show them around the Paris sites such as the Eiffel Tower,the Arc du Triomphe and even my favorite ice cream place,Amorino, was an amazing memory for us all !Despite the fact that I felt the slight pressure to make sure the weekend went smoothly,even the heavy rain failed to dampen our mood.

    Therefore, while it can be difficult being away from home and potentially missing big family moments,there are ways to avoid the sadness and find a way to make the best of your situation to create an unforgettable memory. Just like the continuing rain while we went up the Eiffel tower, every cloud has a silver lining, because then we got the funniest photos ever!

同类题5

阅读理解

    Climate change has had a number of effects on cities around the world, including rising see levels. And, this has become an especially big problem for coastal cities. City officials must now prepare for higher tides on their coasts. The American city of Miami is one example. Located in South Florida, Miami is home to nearly 3 million people and billions of dollars in land and buildings.

    Miami is one of the cities in America most at risk for rising sea levels. The waterfront is central to Miami's culture and economy. But as the seas rise with climate change .the water will not stay put. Large parts of South Florida are in danger of being under water in the coming years. Across Biscayne Bay, the City of Miami Beach is making improvements - raising streets, adding water pumps and more.

    It is costing the city a lot of money. Local communities will spend 500 million dollars for the improvements. Thankfully, the residents, the folks that are paying the bill for this work, realize that the cost of doing nothing is much greater. A possibility officials are discussing with residents is for city to buy homes in some places where flooding has been a problem. The city would then turn that land into parks of grassland that could hold the water.

    Over time, the city may need to take bigger risks. Miami's future depends largely on how much, and how fast, the oceans rise.

    Caroline Lewis leads the climate activism group, the CLEO Institute. She says cities cannot avoid the need to move inland. But, she says,a well-planned withdrawal (撤退) could include measures to keep people safely in place for as long as possible. And, she says, the world could learn from such a model. In these two Florida cities built on wetlands, there remains a lot of hopefulness.