With a lot of difficult problems_____, the newly-elected president is having a hard time. 

_____ the child to bed, she began to correct the pupil’s exercise.

Don’t leave the water ________ while you brush your teeth.　

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

She would move quietly up to the sparrow on a small tree just to get a better look, her face __________ with childlike expressions at one of God’s simple wonders.