当前，全球所面临的重大环境问题的中心问题是___________。

肉眼血尿是指每升尿内含血量超过
A．1mlB．2mlC．3mlD．4mlE．5ml

Years ago our cities were full of cars, buses and trucks. Now the streets are completely congested (拥挤的) and it is very difficult to drive a car along them. Drivers must stop at hundreds of traffic lights. What are our cities going to be like in ten or twenty years？ Will enormous (巨大的) motorways be built across them？ With big motorways cutting across them, full of noisy, dirty cars and lorries, our cities are going to be awful places. How can we solve the problem？There are some good ideas to reduce the use of private cars. In 1989, for example, the authorities in Rome began an interesting experiment: passengers on the city buses did not have to pay for their tickets.In Stockholm there was another experiment: people paid very little for a season ticket to travel on any bus, trolley bus, train or tram in all the city.In many cities now some streets are closed to vehicles, and pedestrians are safe there.In London there is another experiment: part of the street is for buses only, so the buses can travel fast. There are no cars or taxies in front of them.What the writer worries about in a big city is ______.
A．the number of traffic lightsB．the shortage of busesC．the lack of motorwaysD．the traffic congestion

The word "arid" is closest in meaning to ______.
A. sunnyB. flatC. dryD. sandy

下列关于关节的叙述，正确的是()
A.关节面、关节囊、关节腔是关节的基本结构B.关节面表面覆盖一薄层骺软骨C.关节囊的滑膜层与纤维膜之间的间隙称关节腔D.关节窝周缘均附有关节唇E.每个关节都有囊内和囊外韧带加强

The counterclockwise swirling of the hurricane is brought about by______.
A．the low-pressure area in the center of the stormB．the force of waves of waterC．the trade windsD．the increasing heat