企业之间通过电子商务达成交易，而（）是电子商务的中心功能，已经成为电子商务的重点。
A.联合采购
B.电子采购
C.集中采购
D.分散采购
参考答案：B
—My little daughter is coughing worse than ever.
—She__________to the hospital yesterday.
A．had to be taken
B．should have taken
C．must have been taken
D．ought to have been taken
使用中的钻孔，必须安装孔口盖。报废的钻孔必须及时封孔。
