My train ___ at 8:30 am, so I ___home at 8:00 tomorrow morning. A.is left; am leaving B. leaves ;am leaving C.is leaving ; have left D.leaves; leave 答案: B有一张长40cm、宽30cm的长方形硬纸,在其四角剪去相同的小正方形,折起来做一个无盖的盒子,使盒子的底面积等于原长方形面积的一半,则做成的长方体的高是
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A.30cmB.5cm或30cm
C.5cmD.10cm