The widespread of super-hybrid rice around the world ______the lives of millions and millions of

people suffering from hunger to a great level. [ ]

A. improved    

B. is improving  

C. has improved  

D. has been improving

材料预算价格的组成包括（）。

A.材料供应价格

B.材料运输损耗

C.材料检验实验费

D.采购人员出差费用