. One third of the area ______ covered with trees. About seventy percent of the trees ______ been planted recently.
Men usually go straight to ________ they want and leave quickly when shopping.
In the reading-room, we found Winifred ____at a desk, with her attention _____on a novel.
No matter where he is, he makes_____ a rule to go for a walk before breakfast.
___ to give up smoking, he threw away his _____ cigarettes.
By the time he retires, professor Baker _____ for almost forty years.