—How unhappy your roommate looks!—Yes, but he's not willing to tell me what it is ________ is troubling him.
______ at the crossing and you will see a tall white building.
Rather than ______ at home playing cards on the Internet, I prefer _______ out for a day trip.
Two-thirds of the land ________ covered with green grass and the rest _______ covered with pine trees.
I feel it is you as well as your wife that for your son’s bad performance at school.
Tom is so talkative. I’m sure you’ll soon get tired him.