You are irreplaceable
无可───can't;取代───replace
Can't you sit still ?───你就不能老老实实坐一会儿吗？
Pete can't go and I can't either.───皮特不能去，我也不能。
They can't have children.───他们不能生孩子。
If I can't obtain a visa to the United States this Jan. , it will be ok with me to go there next fall.───如果我不能申请到今年一月去美国的签证，那么明年秋天去也可以。
A screen full of colors, toolbars, and windows is the sort of visual noise you can't afford to have around when writing.───一个充满颜色，工具栏和视窗的屏幕是一种你写作时无法忽略的视觉干扰。
If you can't figure it out, write that down, too, specifying exactly where you fell off the train.───如果你无法作到这点，把差异也写下来，准确说明在哪儿你脱离了轨道。
You can't make bricks without straw.
Please speak more clearly, we can't hear you.
I can't. I have a test tomorrow.
You can't eat your cake and have it.
You can't teach an old dog new tricks.