—I drove to Zhuhai for the air show last week.
—Is that ________ you had a few days off ?
A．where B．when C．what D．why
What is even more important is______ the earth cooled down, water began to appear on its surface.
A．that B．that as C．which D．which as
His idea was such a good one ______ we all agreed to use it.
A．as B．that C．so D．but
Although the causes of cancer_____, we do not yet have any practical way to prevent it.
A．are being uncovered B．have been uncovering
C．are uncovering D．have uncovered
With just four years _______, the Brazil Olympic organizers have promised to deliver an equally inspirational ceremony.
A．gone B．to go C．going D．go
We are so sorry for that．We'll try to determine exactly _________ went wrong that evening．
A．where B．what C．which D．how
