Mr. Chen spends more time than he used to games with his child after work.
A:playing
B:play
C:played
D:plays
如图装置可以完成多个简单实验,具有药品用量少、实验现象明显、尾气不外逸等优点。
化简-3227的结果是( )
使用显微镜对光时,下列哪些结构应在同一条直线上( )