—The research on the new flu virus vaccine is challenging and demanding. Who do you think can do the job?     —_______ my students have a try?

We find ------interesting to learn history.

We         arrive at six. But I’m sorry we are late. 

—Hurry up, Mum. The lights are turned on. Dad has been back.—It _________ be him. He has gone to Shanghai.

— Must they clean and tidy the classroom now? — No, they      . It       after school in the afternoon.