. We called the First-Aid Center ____ the traffic accident happened.
The teacher talked in a very low voice_____make himself________, clearly.
________is well known that great changes have taken place in China recently.
The path______the park is lined with many trees.
The number of people invited_____40, but a number of them______absent for different reasons.
Don't forget to take a breath of____fresh air and have some exercise each day. It will make_____difference.