原式=2a-3b-3a
=-a-3b.
故答案为:-a-3b.
进行多个厂址或选线方案的优选时,应对每个选址或选线方案进行( )。
A.敏感生态问题预测
B.自然资源预测
C.生态系统整体性预测
D.环境影响预测
The lower room was in darkness, but by _____ his way he found the bag.
A.taking
B.feeling
C.pushing
D.making