I’m sorry I didn’t phone you, but I’ve been very busy ____ the past couple weeks.
It is so cold that you can’t go outside _____ fully covered in thick clothes.
As you go through this book, you ________ that each of the millions of people who lived through World War II had a different experience.
It was when we were returning home ________ I realized what a good feeling it was to have helped someone in trouble.
______ scientists have learned a lot about the universe, there is much we still don't know.
If you come to visit China, you will ______ a culture of amazing depth and variety.