Ⅰ. Fill in the blanks according to the given tips, using their proper fo rm.
1. It’s a _____(遗憾) for me not to help you.
2.—M ay I use your _____(相机)?
—Sorry, I have lent it to Tom.
3. Bob is the oldest _____(在……其中) the four boys.
4. We are living in the 21st _____(世纪) now.
5. Please _____(检查) your paper again.
