将一张长20厘米、宽12厘米的长方形纸片沿对角线折叠,得到的图形如图1,再将该图形过图1所标示的B点折叠,并使得A与A重合(同时C与C重合),得到四边形ABDC,如图2,则四边形ABDC的面积为多少?( )
A campus emergency ______ occur at any time of the day or night, weekend, or holiday, with little or no warning.
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