If you are not sure how to use the words, you may ______ the words in your handout.

Such a good opportunity may not come again, so you ____________ let it go this time.

Did he come back early last night—- Yes. It was not yet eight o’clock _______ he arrived home.

Thousands of people illnesses in dirty hospital in the 19th century.

, which has been widely used in________ recent years, is ________ good way of ________ communication