检查某班l5岁学生50名,其中龋病者10人,龋失补牙数为:D=70,M=2,F=8,龋失补牙面数为:D=210,M=10,F=15,这班学生龋面均为( )。
A campus emergency ______ occur at any time of the day or night, weekend, or holiday, with little or no warning.
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