The athlete's years of hard working________when she finally won the Olympic gold medal.

 With the development of Chinese economy, many unexpected problems have ________; for example, the prices of our daily goods and housing are ________ sharply.

Having lived in China for 8 years, Helen has a good ____________ of both English and Chinese.

The police _______ the stolen jewellery and returned it to the owner.

Because of the recent bad weather，the work is several weeks behind ______.