It is difficult __________ a best friend.
The train __________ she was travelling was late.
—Howdo you like the book? —It's quite different from __________ I read last month.
Is this the museum __________ you visited the other day?
I refuse to accept the blame for something __________ was someone else's fault.
This is the small house—less than 15 square meters, under __________ roof lives a large family of three generations.