继电器、接触器、开关的触点应（）。
A.动作灵活
B.接触紧密可靠
C.无锈蚀
D.无损坏
参考答案：A, B, C, D
Of the following signs and symptoms of bowel obstruction, which is related primarily to small bowel obstruction rather than large bowel obstruction
A. Profuse vomiting.B. Cramping abdominal pain.C. Abdominal distention.D. High-pitched bowel sounds above the obstruction.
酸性最强的是（）
A．茜草素
B．2，5-二羟基蒽醌
C．1，8-二羟基蒽醌
D．2，6-二羟基蒽醌
E．1，4-二羟基蒽醌
