It’s helpful to put children in a situation ________ they can see themselves differently.

Would you please ______ the paper for me and see if there are any obvious mistakes?

Scientists are convinced _____ the positive effect oflaughter _____ physical and mental health．

Such a good opportunity, once ______, might never come again.

I’m surprised to hear that Sue and Paul have ________.— So am I. They seemed very happy when I last saw them.[ ]