A lion ____ only attack a human being when it is hungry .
9. Which of the following is not a flying machine?
10. As middle school students, raising pet ______ all day long is a sheer waste of time.
11. Don't judge a person only by his _____.
12. --- What's on tonight? --- I hear there is going to be a pop song contest. A group of famous singers from Hong Kong and Macao are ____ in our village theatre.
13. The voyage diaries were handed down by his great grandfather, so their brothers have kept them as ____ .