By the time I locked the door, I realized I ________ my keys at home.
You had better__________because you have to drive back home.
The government of Yancheng is building_________cheap and good houses for the people.
—________that China has the largest number of iphone4s users now.— I believe so.
Drivers are warned___________when they are tired.
—Is this ___________ruler? —No.________________is over there.