—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

单项选择题—What's the matter with you —After the long walk, my leg ______ and I couldn't go any further.

单项选择题Many people keep dogs as pets because dogs are regarded as（）friends to people.

A. lonely
B. only
C. loyal
D. fair

单项选择题Friendship helps us understand ______ we are, ______ we need each other and ______ we can do for each other.

单项选择题—Mum, it is nice weather. I want to skate this afternoon. —Don't you think the ice on the lake is too thin to ______ your weight

单项选择题One day Chuck is on a flight ______ the Pacific Ocean suddenly ______ his plane crashed.