The reason ______ the delay is ______ we have had difficulty in obtaining materials.

— Have you been to the Great Wall? —Perhaps not in my memory. ________, it might have been during my early childhood.

___is no doubt that the Dallas Mavericks will defeat the Washington Wizards in the next game.

The crowd cheered wildly at the sight of Liu Xiang,who was reported _______ the world record in the 110-meter hurdle race.

It was the first time in my life _______ I had experienced the UK.