---_______ they stop to have a rest? ---No, let them go on.
Such a custom came into _______ long ago.
His parents wouldn’t let him marry anyone ______ family was poor.
He attends the evening class ____, that is, Monday, Wednesday and Friday.
Many tall buildings _______ in Shanghai in the past few years.
We were running out of gas. I went off ____ a service station where I could buy some gas.