1, Peter, whom I had seen before, wasn't at the party.

3,  John, whose grades are the highest in the school, received a scholarship.

4,  There are thirty students in the class most of whom are with me at secondary school

5, Most of the people whom I invited to the party couldn't come

6, Two people whom I didn't know walked to the classroom

7, The teacher whom I studied with last year no longer teaches in our school

8, The flight which we wanted to travel on was fully booked

9, Why does she always wear clothes which are too small for her?

10,  Did you enjoy a party which you went to?

11,  The chair on which  we were sitting wasn't very comfortable

12, The student with whom I share the room is honest

13, Hoan Kiem Lake, whose water is always blue, is a historical place.

14, Mrs. Jones, whose son won the scholarship last year, works at Orion company

15,  We are visiting the children whose parents died in the storm.