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。
