—It's not difficult for five workers to push the broken van away.

— Yes, __________.

把0.05 mol NaOH固体，分别加入下列100 mL溶液中，溶液的导电能力变化不大的是(　　)①自来水②0.5 mol·L^－1盐酸　③0.5 mol·L^－1醋酸 ④0.5 mol·L^－1 NH₄Cl溶液

请认真阅读下列短文，从短文后各题所给的A、B、C、D四个选项中，选出最佳选项。
A
    If you travel by air across the center of Africa or South America, you fly over forests for thousands of kilometers. These great forests are the oceans of trees. There are full of thousands and thousands of different kinds of plants and animals.
    However, the world's forests are getting smaller all the time. We are cutting down the trees because we need wood, and we need more farm land. Some people say that there will not be any forests like these in 20 or 30 years. what will happen if they disappear?
    If we cut down our forests, a lot of plants and animals will disappear from the world. In a lot of places the new farm land will soon look like the old deserts. Crops will not grow there. It will not rain very often, and the weather will get very hot. Perhaps the climate of the world will change. This will be dangerous for everyone in the world. That is why we must take care of our forests.

汽车安全带是一种有效的安全防护装置，被誉为“生命带”，可以防止人在交通事故中受伤或减轻受伤程度。驾乘人员系好安全带，在事故中存活的机会是不系安全带的2倍，还可以将受伤的机会降低50%。可见开车坐车养成系安全带的习惯有利于（　）

如图，在△ABC中，∠C=90°，∠B=30°，以A为圆心，任意长为半径画弧，分别交AB、AC于点M和N，再分别以M、N为圆心，大于$\frac{1}{2}$MN的长为半径画弧，两弧交于点P，连结AP并延长交BC于点D，下列结论：

①AD是∠BAC的平分线；②∠ADB=120°；③AD=BD；④DB=2CD．

其中正确的结论共有（　　）

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