—The research on the new bird flu virus vaccine is challenging and demanding. Who do you think can do the job?—____ my students have a try?
If ____unsolved, the problem of food safety may lead to more serious results.
Jack is late again. It is ____of him to keep others waiting.
Though________money, his parents managed to send him to university.
It’s funny that Howard___ speak to you like your boss.
Helen has ____French and can speak fluently after a short stay with her aunt in Paris.