this these those的用法和區別

例句：

This knife needs sharpening.

這把刀需要磨了。

This material frays easily.

這布料容易磨損。

Those laws no longer pertain.

那些法律已不適用了。

These questions frustrated me.

這些問題使我懊喪。

These injuries were avoidable.

這些傷病本是可以避免的。