【单选题】
下面轴端面上“中心孔”的标注错误的是
①
<img src=https://mi-public.oss-cn-hangzhou.aliyuncs.com/mssvc/editor/image/2018/07/03/1530604496915719.bmp title=1530604496915719.bmp alt=t7-4 轴类零件-A.bmp style=max-width: 100%; max-height: 850px; white-space: normal;/>
②
<img src=https://mi-public.oss-cn-hangzhou.aliyuncs.com/mssvc/editor/image/2018/07/03/1530604602791630.bmp title=1530604602791630.bmp alt=t7-4 轴类零件-B.bmp style=max-width: 100%; max-height: 850px; white-space: normal;/>
③
<img src=https://mi-public.oss-cn-hangzhou.aliyuncs.com/mssvc/editor/image/2018/07/03/1530604645538638.bmp title=1530604645538638.bmp alt=t7-4 轴类零件-C.bmp style=max-width: 100%; max-height: 850px; white-space: normal;/>
④
<img src=https://mi-public.oss-cn-hangzhou.aliyuncs.com/mssvc/editor/image/2018/07/03/1530604663594325.bmp title=1530604663594325.bmp alt=t7-4 轴类零件-D.bmp style=max-width: 100%; max-height: 850px; white-space: normal;/>