The girl was often heard _______ happily in her room.
Which sign means you can’t drop litter?
We ________ not to go that way because the road ________.
I used ____ papers and watch TV after dinner. But now I’m ________ a walk.
We should be strict _____ ourselves ____ our work.
The number of the children in the school ________ about three hundred. ________ of them________ from the countryside.