A:早春黄河中渐渐消融的冰凌﹣﹣熔化
B:夏天的清晨草坪上附着的露水﹣﹣液化
C:深秋的霜冻﹣﹣凝华
D:冬天空中飘落的雪花﹣﹣凝固
The teacher asked us to ____ ____ some chalk.
一座拦河坝的横截面是个梯形,它的面积是72平方米,它的上底是12米,下底是18米,这座拦河坝的高是____米?