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When did her mother go back to work（）
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胀管率应在1.5%～3%范围内。( )
All over Europe, and in North America, there're lakes and forests which are dead or (1) and the (2) is thought to be acid rain. What is acid rain Mr. Justin Cook, a scientist, explains: "All fossil fuels, (矿物燃料)，that (3) oil, coal and gas, contain sulphur. When these are burnt, for example (4) motor vehicles, they form sulphuric acid (硫酸)This (5) UP into the air, and soon it falls back to (6) , into lakes and (7) trees in forests." This can cause many local problems. (8) a result, lakes become acidic, fish disappear and trees are killed. The pollution is carried great distances by the wind, so sulphuric acid (9) in Britain can travel as far as Scandinavia (斯堪的纳维亚). Czech is one of the countries with the most acid rains and large areas of (10) consist only (11) dead trees.Is there (12) that can be done about acid rain Mr. cook says: "The rain (13) of acid rain is (14) power stations to install filters that (15) the acid getting out into the air. Here in Britain, the only (16) that has been taken is that the chimneys are built (17) so that the pollution is more distributed." If the petrol used in motor vehicles (18) lead--free, then it Would be possible to filter exhaust fuses (废气) which are a (19) cause of pollution. But these filter mechanisms (机械装置)can not work (20) the leads is removed. 10（）
Passage 2In about two years, NASA astronauts will go into space with personal assistants. Robotic assistants, of course. About the size of softballs, these personal satellite assistants (PSAs) can float throughout the space shuttle or space station, automatically monitoring life support systems, snapping photos, and taking over monitoring tasks from failed sensors. They're equipped with collision avoidance system so they won't bump into anything Naturally, they're wireless. Thanks to their videoconferencing capabilities, the PSAs offer a virtual presence for ground crews and scientists, letting them advise astronauts--in real time --in the midst of their experiments. The PSAs. will be stowed until the spacecraft reaches orbit (天体运行的轨道). And then activated by the astronauts, ground crews, or even by the spacecraft itself or other PSAs requesting help, they can work automatically or respond to voice or radio commands, and can exchange information with the spacecraft's main computers.Floating through the spacecraft, the little robots will measure gas levels, temperature, and atmosphere pressure--making them ideal for checking alarms and dangerous areas, such as the compartment that caught fire on the Mir space station. And, if "smart" identification tags are added to inventory items like food pouches and experiment samples, project manager Yurt Gawdiak of NASA's Ames Research Center says PSAs could track inventories.One of their biggest benefits may be size. By squeezing into hard-to-reach spaces of the shuttle or space station, PSAs can go where no man has gone since the vehicles were first assembled--simply because man doesn't fit. Which of the following statements is NOT true according to the passage（）
不锈钢管具有较高的电极电位、表面致密的氧化膜和均匀内部组织，以及很高的耐蚀性能。( )
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