16. The river, ______the bank are covered with trees, is very long.
The yellow house ________ windows face south is the place ________ I spent my childhood.
Because Sarah has always saved __________, she is now able to afford a big house.
--Reading is the best way to pass time on the train. --, I never go traveling without a book.
When it ________ air pollution, Beijing faces the three “C”s, cars, coals and construction, which lead to Beijing’s thick air pollution.
It remains ______ whether Jim will be fit enough to play in the finals.