31. _______ with the present situation, the local government could not find effective measures to reduce the risk of coal mine accidents.
________by curiosity,he opened his wife’s notebook and began reading her diary.
________ the delayed flight will take off depends much on the weather.
I________ along the street looking for a place to park when the accident________.
Not until_______ home ______he had had his wallet stolen.
Playing on a frozen sports field sounds like a lot of fun. Isn’t it rather risky, _______ ?