题目

It has been announced that passengers ____ remain in their seats until the dangerous subjects have been removed. A. can      B. will      C. may        D. shall 答案：D 解析: shall在此表示“命令、警告，强制”淡之意。如图，菱形ABCD，点O是对角线AC上的一点，且OA=AB，OB=OC=OD，则∠BAD的度数是72°72°．