1/ who lives next door
2/whom I met yesterday
3/ whom I met at the meeting
4/ which is next to my office
5/ which I visited yesterday
6/ whose mother is my teacher
7/ which is in south-east Asia
8/ which come from Australia
9/ who lives on Trang Tien street
10/ that you gave me on my birthday
11/ who first walked on the moon
12/ that I bought yesterday
13/ who sings very well