通过2mm筛较多的粗粒料，具体用何种方法进行筛分？并说明原因。

《招标投标法》规定，依法必须招标的项目，招标人应当从确定中标人之日起( )日内，向有关行政监督部门提交招标投标情况的书面报告。

A．7
B．15
C．30
D．45

—We were surprised to hear that the reason_______ she gave for her absence was______ her mother was ill.

—Yes，we saw her mother was at the supermarket that morning.

A．why；that

B．which；that

C．that；because

D．why；because

在模型间为保证职工有一个良好的文明生产环境，一般都装有除尘设备，该设备主要由吸尘器、风管组成。

材料产生不能恢复的变形的性质称为（）。

A.塑性变形

B.弹性变形

C.弹性

D.塑性

桃仁承气汤2功效与作用