______ which university to attend, the girl asked her teacher for advice.
I still remember the days __________ I spent __________ with you in Beijing.
To do it by yourself is more important than __________.
In my opinion, life in the twenty-first century is much easier than __________.
__________ she finds out that you've lost her book?
After a new reform, the number of the products in the factory is now __________ it was in 2003.