组合开关动触头由两片铜片和绝缘纸板铆合而成，其结构有90°、180°。两种。
参考答案：对
Passage One
What is happening to Barbados’s sugar industry a. It is prosperous and stable. b. It has vast expanses of deserted cane fields. c. It uses cane fields as tourist attractions. d. It stopped growing sugar 30 years ago.
试简述影响浓缩塔精馏的主要因素？
