某单位员工为“5?12”四川汶川大地震受灾者捐款,其中20%的人捐助100元,40%的人捐助200元,25%的人捐助300元,其余捐助500元以上,则这组数据的众数是( )
A campus emergency ______ occur at any time of the day or night, weekend, or holiday, with little or no warning.
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