this和these的读音怎么分辨（this 与these 发音区别）

读音分辨: /ðɪs/，/ðiːz/

This is the one I want.

这就是我要的那个。

This suggestion dumbfounded Joe.

这个建议使乔伊惊呆了。

This knife needs sharpening.

这把刀需要磨了。

This suitcase doesn't lock