测量计算的基准面是什么？
参考答案：
参考椭球面。
He__________ he would be able to leave tomorrow, but it's beginning to took difficult.
A．hopes
B．was hoping
C．had hoped
D．hoped
不同分子大小的蛋白质混合物流经凝胶柱层析时，小分子物质因体积小最先被洗脱出来。 ( )
