People have always been curious ______ how living things on the earth exactly began

Beijing government puts more than 700 million yuan to increase its green space this year; ____________ doubles the money provided last year.

When he knew that he had passed the driving test, he smiled _______.

At present, more and more people prefer_________ in the countryside because there is _____ pollution in the city.

What a journey! We’ve finally arrived!––_____ an out-of-date train schedule, we would not have missed the train.