—You may find the key to the math problem on page 107.—Ah, it’s so simple. I wonder why I _____ of that.
—What are you busy ___? —I’m busy ___ a letter to my mother.
There’s somebody walking behind us. I think ___.
The girl devoted all her free time she had __ others.
—Jane, see, what did I find? —Oh, my lost keys! ____.
Jack, it’s __ bad manners to blow your nose at ___ table.