1. i know she is sad. when/why/which.
2. where's the milk i bought yesterday? which/who/where.
3. the north pole is the place_ santa claus lives. where/when/that.
4. this is a man_ _son is a famous scientist. who/whose/which.
5. i'll never forget the day i met you! where/which/when.
быстро

1. I know why she is sad. When/why/which.

2. Where's the milk which I bought yesterday? Which/who/where.

3. The North Pole is the place where Santa Claus lives. Where/when/that.

4. This is a man whose son is a famous scientist. Who/whose/which.

5. I'll never forget the day when I met you! Where/which/when.