I can try and give you some examples, with their Japanese counterparts, if that helps? What = 何　 What did you do yesterday? 昨日何をしましたか。　What is this used for? これは何で使いますか。 What time did you get home? 何時に帰りましたか。 Which　＝どちら　。Which is better for you, Tuesday or Wednesday? あなたには火曜日か水曜日かどちらがいいですか。　Which book is mine? どちら本は私のですか。 That can be　any of the following, depending on context: それ、あれ、その、あの。That is my book それ「あれ」は私の本です。　That house over there is new。 あの家は新しいですね。　 That is also used a lot in relative clauses - this is the book that my mother bought - これは母が買った本です。 I hope that has helped a little bit - sorry if my Japanese isn't exactly right - hopefully you can still understand the meaning!

Hello Emiko, For a general rule we us 'who' for people - This is the man who you were talking about, 'which' for things - This is the book which he wrote, if this is essential information then you can use 'that'. We use 'where' for places - This is the place where we met. 'When' for times - It is a time when we meet our friends. And 'whose' for possessions - be careful possessions are not just things - they can also be people and animals -This is the lady whose children speak English. Hope this helps. Bob