下列说法正确的是
A．浓硫酸在常温下可迅速与铜片反应放出二氧化硫气体
B．在含有Cu(NO3)2、Mg(NO3)2和AgNO3的溶液中加入适量锌粉，首先置换出的是Cu
C．能与酸反应生成盐和水的氧化物一定是碱性氧化物
D．将Ba(OH)2溶液滴到明矾溶液中，当SO42-刚沉淀完时，铝以AlO2-的形式存在
答案：D
A不正确，反应需要加热；银离子的氧化性强于铜离子的，首先析出银，B不正确；C不正确，例如氧化铝也能和酸反应生成盐和水，但氧化铝是两性氧化物；因此正确的答案选D。
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| It is well known that the English go out with an umbrella or a raincoat. Why? 1 the weather in Britain often changes quickly. It is not very usual for the same kind of weather to 2 long. Spring can be rainy or windy, 3 the weather is getting warmer and you can hope more sunny days. In fact, there 4 as much sunshine in spring as in summer. Summer is 5 time for visitors to go to the seaside and other places of interest. The weather can be sunny and nice. People often go out to have a walk or swim. Fall is a beautiful season 6 trees in the woods and parks changing color. During fall it is still nice to be outside, too. In winter, it gets colder. It might snow, especially on high land and in the north. There are 7 very high winds in this season. January and February are the coldest 8 of the year, while the warmest 9 often July and August. The difference 10 temperature between winter and summer is not so great, winter is about 45℃, and for summer about 15.5 ℃. | ||||
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