固定管板式换热器的特点有()。
A.结构简单
B.制造成本低
C.管程易清理
D.壳程易清理
参考答案:A, B, C
Some people argue using _______ nature to meet our own needs may spell disaster, unless we start to look around and understand how _________ clean environment benefits us all.
A.the; a
B.the; the
C./; a
D.a; a
自动电压调节器按用户要求可以全部或部分装设的附加功能有哪些?