恒速干燥阶段，物料整个表面都有非结合水份，表面的蒸汽压与同温度下水的蒸汽压（）.
参考答案：相等
用长为20cm的铁丝，折成一个矩形，设它的一边长为xcm，面积为ycm2．
（1）求出y与x的函数关系式．
（2）当边长x为多少时，矩形的面积最大，最大面积是多少？
-Did you punish him for losing your digital camera?
-Yes, but I don't think I ________.[ ]
A．should do that
B．need to have done so
C．ought have done that
D．should have done so
