---___________ tall building it is! ---It has over one hundred floors.
_______ necessary for us _______ our environment clean and tidy.
She was afraid of __________SARS because it was dangerous.
-----Who taught _________Japanese?----I learned it by ______________.
Humans can’t live _______air.
---Oh, you have a headache and a cough. _______have you been like this?---Three days.