. --- Sarah said she wrote you a letter. --- I wonder ______ she is writing to me about.

Knowledge from real life isn't easier to forget than ___ achieved from textbooks．

Generally speaking, clothing made of man-made fibers is less superior than _______ made of natural fibers like cotton, wool or silk.

-- Do you have any more bags of this size? -- I’ sorry we’ve sold ________ but this one.

—Shall I attend my friend's coming­of­age ceremony, Mum?—No, unless you see to ________ that you will be home before 1000 PM.