-- _____is that used for?---_____ the floor.
To keep healthy, Professor Johnson ____ cycling as a regular form of exercise after he retired.
Tough ______ _money, his parents managed to to send him to a key university.
She ____________ the path as the trees around her became thicker.
Once ________ more attention, the little trees could have grown better.
After ten hours’ operation, the doctors managed to _____the one-year-old twins at the head.