One way for students to prevent H7N9 flu virus is to open the windows of the classroom to allow the air to ________.
Our teacher is always busy preparing lessons until 11 o’clock at night,______we students have gone to sleep.
The news______is spreading around the airport is______ a heavy storm is coming.
He is taller than he______.
If you stand here, you’ll get a better______of the river.
Let’s keep to the point, or we______ any decisions.