题目

－The door was open.  －It ______ open. I had locked it myself and the key was in my pocket.   A. can not be             B. must not be                     C. can not have been      D. must not have been 答案：C 如图，数轴上点A对应的数为2，AB⊥OA于A，且AB=1，以OB为半径画圆，交数轴于点C，则OC的长为（　　） 　 A． 3 B． C． D．