易燃易爆作业场所不可使用下列哪种防护用品？（）
A．底面钉铁件的鞋
B．棉布工作服
C．防静电鞋
参考答案：A
My sister_______ the League last month and she has decided to _______ the activity to help the aged next week.
A．joined; join in
B．took part in; join
C．joined; attend
D．joined in; join in
在Excel中，用键盘来选择整个工作表的组合键是（）。
A.Ctrl+Shift+Space
B.Ctrl+Alt+Del
C.Ctrl+Alt+Backspace
D.Ctrl+Alt+PageUp
