---________ do you do exercise ?---Once a week .A. How long B. How often C. How soon
---Someone is knocking at the door. Who may it be? ---It ______ be Tom. He is still in the school.
---Have you seen Dr. Adams recently?---No. He __________ Hong Kong for an important meeting. He’ll come back tomorrow.
--- Would you come back to have dinner with us this evening? --- I’d love to, ______ I have an important meeting .
There __________great changes in our hometown in the past fifteen years.
-----________did your uncle leave his home town ? ----He ___________for nearly twenty years.