A lot of trees ______ on the hill yesterday.
---Who is the tallest boy? ---It ______ be John. John is of medium height.
These young trees must ______.
I found ______ not very difficult to keep away from the A/H1N1 Flu.
A tourist will easily lose his way in Beijing ______ he has a map or a guide.
---I heard you bought a flat in the countryside? ---Yes. I ______ the quiet country ______ the noisy cities. Besides, houses are cheaper.