On account of the development of the  economy, the environment is seriously polluted and we must

________ the emission of the carbon dioxide.[      ]

A. cut in      

B. cut off

C. cut up  

D. cut down

以下哪项属于有效投标（）。

A.资格预审后，联合体增减人员

B.投标人逾期送达的投标文件

C.投标人未提交投标保证金的投标

D.投标文件加盖公章并密封严实