The students ___ busily when Miss Brown went to get a book she ___in the office.

In _________to being used in industry，laser can be applied to operations in the hospital.

People should be cautious ______their personal information when surfing the Internet so as to prevent certain computer viruses ______ it.[ ]

“ When is your birthday ” “ My birthday is ______ May 2nd .

I find difficultfor Tom to reach that picture.He is a little short.