苯丙胺类是一种强烈的
A．致幻剂
B．中枢神经抑制剂
C．中枢神经兴奋剂
D．β-受体阻滞剂
E．H2-受体拮抗剂
参考答案：C
已知三角形面积为1，外接圆面积为π，则这个三角形的三边之积为( )
A．1
B．2
C．3
D．4
The (72) is a system for linking hypertext documents Originally, each document was a page written in (73) with hyperlinks to other documents．Nowadays，XML is gradually starting to take over from (73) ．
A．Web B．E-mail C．DNS D．FTP
