Tom first met Lucy three years ago. She ____ as a teacher in a high school. A has worked B was working C is working D had worked
It was at four o'clock in the afternoon ____ he and his grandpa reached the museum in Guanghan.
I consider____ my duty to help you.
Is_possible to fly to the moon in a spaceship?
Is_necessary to tell his father everything?
There is a photo on the wall.____ the photo of Lei Feng.