北宋在统一全国的过程中采用了( )战略。
A.先南后北
B.先北后南
C.中间突破
D.双管齐下
参考答案:A
His new book___ next month.
A.will be published
B.is publishing
C.is being published
D.has been published
水一旦溶解了大量二氧化碳,会对输送的碳钢管道造成严重的酸性腐蚀。