On top of the mountain ______, which was built 2,000 years ago.
Professor Li is the person to ____________ you should write.
Do you know the reason _______ he was late?
I’ll take you to the museum ______ you may see everything _________ you want.
Is oxygen the only gas ________ helps fire burn?
The number of the people present at the concert was _____ than expected. There were many tickets left.