—The 2010 World Expo of Shanghai is ___ first time for the world to be hold in developing countries---Yes. All of us want to have ___ second time to hold it.
I don’t know _____ or not he will come . _______ he comes , I will call you .
The robot needs _______ once a month. And we will check it for you for free.
We didn’t know how to find them because they didn’t tell us _______.
In order _______ his English,he joined an English club.
Don’t make the students _______ this or that . They are busy.