It has always been the _____ of our firm to encourage workers to take part in social activities.
It's not rare in __________ that people in __________ fifties were going to college for further education.
Many students __________ going online because they can gain much fun.
The stubborn boy didn't __________ so he missed the chance.
The post office is quite __________.
To understand the grammar of the sentence, you must break it __________ into parts.