My father began to work ______ a bus driver when he was 20 years old.

A clean environment can help the city bid for the Olympics, which _______ will promote its economic development.

During that frightening war, these foreigners fought _______ us ________ the enemy. 

?I think the company may not offer you a good pay.  - ______ , I won’t take the job.

For holidays, many people visit the Great Barrier Reef _____ the northeast coast of Australia, which has 700 islands.