加氢装置反应器积垢篮一般安置于（）
A、每个催化剂床层的顶部
B、反应器催化剂床层的顶部
C、每个催化剂床层的底部
D、反应器催化剂床层的底部
参考答案：B
One reason that criticism has been leveled at derivatives and derivatives markets is that:()
A. derivatives have too much default risk.
B. markets for derivatives seldom function efficiently like a stock exchange.
C. they are complex instruments and sometimes hard to understand.
工业用热电阻是接触式测温仪表。
