B12的基本构造与
A．胆固醇
B．血红素
C．胰岛素
D．以上皆非
参考答案：B
His uncle's son wants _____. [ ]
A. joining the club
B. join the club
C. join in the club
D. to join the club
PowerPoint中用鼠标连续选取多个选项时用什么键（）
A.按下Enter
B.按下Alt
C.按下Ctrl
D.同时按下Ctrl和Alt
