Our headmaster suggested    a discussion on the subject.

It's clear that the thief was seen __ into the room that night.

________ thousands of Chinese students，Chuck has vast experience in the Chinese class.

The sights of Nanchang never fail to _______ foreign tourists, making them abandon themselves to the beauty of the city.

Since then, more than 2 billion apps have been downloaded at prices ________ free to $900.