1)介詞后面的關(guān)系詞不能省略。

2)that前不能有介詞。

3) 某些在從句中充當(dāng)時(shí)間，地點(diǎn)或原因狀語(yǔ)的"介詞+關(guān)系詞"結(jié)構(gòu)可以同關(guān)系副詞when 和where 互換。

This is the house in which I lived two years ago.

This is the house where I lived two years ago.

Do you remember the day on which you joined our club?

Do you remember the day when you joined our club?