______ for a long time, but he managed to catch up with his classmates at last.
Titanic is the most exciting film _______ I have ever seen.
______ has helped to save the drowning girl is worth praising.
Although the working mother is very busy, she still ______ a lot of time to her children.
When you are learning a foreign language, _______, you must forget your own language.
Great changes _______ in the city, and a lot of factories _______.