—Did Bob hurt badly that day? —_______ . He didn’t come to school these days. A. No, he didn’t B. I’m afraid not C. I’m afraid so D. Yes, he was 答案:C如图是一款人脸识别门禁一体机,通过摄像镜头捕捉人脸信息,并将所拍图象与系统教据库中预先录入的人脸照片模板进行比对.该摄像镜头相当于 镜,成一个 立,缩小的实像,若要拍摄镜头前1m处的人脸.它的焦距应小于 cm.