The problem of the polluted river _____ right away to prevent possible danger to the local people.[ ]

A. should be solved

B. should have been solved

C. may be solved

D. might have been solved

施工成本计划的指标应经过科学的分析预测确定，可以采用( )等进行测定。

A．对比法

B．计时观察法

C．实验法

D．因素分析法

E．询问法