---Do you know the famous scientist Yuan Longping? ---Of course. His name______whenever the matter of hybrid rice(杂交水稻)is discussed.
—What did he say? —He asked _____ for the book.
It was the first time that Mary _____a play , so she felt a little nervous.
The old man walks_____ dog after _____ supper every day.
My suggestion is that he _________to see a doctor at once.
Helen had to shout ________above the sound of the music.