While reading, Helen has a habit of stopping _____ to give her long and flowing hair a smooth

we were listening to the speechattentively, a voice _____ to announce the result of the election.

He found it increasingly difficult to read, ______ his eyesight was beginning to fail.

_______may I keep this book –For two weeks.

Under the Dome, a documentary self-funded by Chai Jing, has rapidly increased ________ public’s awareness about ________ air pollution.