— Must I turn off the gas after cooking?— Of course. You can never be________ careful with that.
My mother_______ if she ________her work this week.
.---My brother fell off his bike and hurt himself. --- .
Environment(环境) is very________,but you don’t understand the_______ of it,you always drop litter everywhere.
He spent as much money as he could _______ a new iphone6.
The teacher told me _________when I left the classroom.