—The current European debt crisis is affecting many countries in the world.—Will it be at least several years __________ everything returns to normal?

It was the first time that I __________ the night face to face.

Rather than ______ on a crowded bus, he always prefers　a bicycle．

We should pay close attention to safety in schools because of frequent reports about accidents ____ students got injured or killed while in school.

______ Marx's works with Engels', and you'll find many differences．