题目

We have sometimes accidents on this line, but no accidents          since last winter. A．occur                                                        B．have occurred      C．have been occurring                     D．are occurring 答案：B等腰三角形的一边长为4cm，另一边长为6cm，则它的周长为 [　　] A．14cmB．16cmC．10cmD．14cm或16cm