一个箱子里有足够多的黑、白、红、蓝四种颜色的小球,每人随意抽三个球,至少有多少人才能保证他们当中一定有两人所抽三个球的花色情况是相同的?( )
A campus emergency ______ occur at any time of the day or night, weekend, or holiday, with little or no warning.
免费的网站请分享给朋友吧