She will tell us that each of us has a role ______ in making the earth a better place to live.
— I must apologize for ________ ahead of time. — That's all right.
He _________ the country record at the sports meeting.
________ the normal condition, he can read 150 words a minute.
The schoolboy regretted ________ after he didn't pass his exam.
What way are you thinking of ________ rid of this kind of pollution?