--What is that on the table?  --Oh, a set of ___________ on the table.

I hear a number of workers in the factory_____out of work.__Yes, and the number _____quite huge.

 One-third of the area ________ covered with trees. About seventy percent of the trees _______ been planted recently.

 _____ were nice to me when I was in the United States.

He says all _______ tried their best and that all that can be done _______ been done.