-Are you familiar with the music? -Yes. There was a time _____ this kind of music was quite popular.
Do be careful with what you are to say. If you ___, you will leave a bad impression.
Come on! The man in charge of the job ___ you have to explain everything is waiting.
I had no one ___ me, for I could deal with it all by myself.
To better understand the English poem, we ___ it into Chinese.
Is it a wonder that _____ little cells can store _____ much energy?