题目

The sound of ________ train can be heard in the steel rail long before its being through the air.  A. an arrived           B. a leaving        C.an approaching       D. a crashed   答案：C菱形和矩形一定都具有的性质是（　　）A．对角线相等B．对角线互相平分C．对角线互相垂直D．每条对角线平分一组对角