It was in 1990 ______ the medicine was tested on human patients.
____you are familiar with the author’s ideas, try reading all the sections as quickly as you possibly can.
Only lately _____ about the dark secrets behind the seemingly-happy marriage of the golf star Tiger Woods.
—Did you listen to the lecture given by the famous herbalist doctor Zhang Wuben? — No, we ______ it. But we had a lot of traffic on our way.
Barrack Obama’s recent visit to the Asian nations clearly sent a message to the world ______ Asia is important in America’s global partnership.
I don’t smoke now, but I ____for almost ten years.