一个小组有10个学生,从中选一个组长,若每个人被选到的机会是相等的,则张明或李华被选中的概率是( ),如果进行两次选举,那么两次都选到张明的概率是( )
A campus emergency ______ occur at any time of the day or night, weekend, or holiday, with little or no warning.
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