串级调节系统就是将调节系统的各个环节串联起来。
参考答案：错
解析：串级调节系统由两个单回路构成，主调节器的输出作为副调节器的给定。
The novels written by the author sell best, but five years ago no one could have imagined how great a role he _____in the literary world.
A．was playing
B．was to play
C．had played
D．played
为了验证社会预防措施的效果常采用以下哪种研究方法（）
A.分析性研究
B.实验性研究
C.理论研究
D.综合评价
E.描述性研究
