The cost of renting a house in central Xi’an is higher than ____ in any other area of the city.
We were about to leave the classroom _____ it began to rain.
Three students in ten will go and _____ to stay in the classroom.
The beef is too expensive. I won’t buy it _____.
The medicine _____ natural plants.
----- I’m going to the States. ----- How long ______ you ______ in the States?