逗號后which引導什么從句

　　Which part of Japan do you come from?

　　你是日本哪個地區的人？

　　There is some noise in the data which needs to be reduced.

　　資料里有一些需要刪除的不適用信息。

　　Which is the largest city in the world?

　　世界上最大的城市是哪個？

　　Which way did they go?

　　他們往哪邊去了？

　　Which features do you look for when choosing a car?

　　你挑選轎車時要著重哪些特點？