sure

‘That’s Sarah’s cousin.’ ‘Are you sure?’

“那是萨拉的表妹。”“你肯定吗？”

‘What time does the show start?’ ‘I’m not sure.’

“表演什么时候开始？”“我说不准。”

My mother, I felt sure , had not met him before.

我敢肯定我妈妈以前从未见过他。