2.
使用计算器时先要按一下开机键,以接通计算器的电源,开机键是( )
a . on" style="max-width:100%;vertical-align: middle;">
b . off" style="max-width:100%;vertical-align: middle;">
c . ac" style="max-width:100%;vertical-align: middle;">
d . ce" style="max-width:100%;vertical-align: middle;">