小明在梳理平行四边形、矩形、菱形、正方形的性质时，发现它们的对角线都具有一个共同的性质，这条性质是对角线（   ）

读一读，选择划线部分发音不同的一项

把一个高6分米的圆柱切成两个小圆柱，表面积增加31.4平方厘米，这个圆柱的体积是（  ）立方厘米。

阅读理解(A)
    My friend，Victor，is a zoo keeper in the National Zoo．His work is very interesting but it is hard．Sometimes it is dangerous，too．Every morning，the zoo keepers have to get up at five to prepare the food for the animals．Each kind of animal eats special food．For example，the lions must be given meat； the deer must be given grass and leaves； and the parrots must be given fruit and nuts．Sometimes some animals won't let the others eat their food．If this happens，each of them must be fed separately（分离的）．
    Every morning each cage （笼子） must be washed by the zoo keepers．This can be dangerous，especially with lions and tigers．To make the work easier，the animals are locked in the sleeping compartments（ 隔间） while the cages are being washed．When the animals are sick，the zoo keepers must look after them．Each sick animal is kept in a separate cage and given medicine．Sometimes they must be given injection．It is not easy to inject a sick lion!
    All the keepers live near the zoo．Each of them has a small house．There he lives with his family．They do not have holidays on Sundays and special holidays．Instead，each of them has a day off during the week．Each keeperhas a holiday on a different day from that of the other keepers．
    The most important job of the keepers is to look after the safety of the visitors．People must be stopped from doing dangerous things．Many people have been hurt because they did careless things，like putting their hands into the lion's cage．

方程x﹣（2x﹣a）=2的解是正数，则a的取值范围是____．