计算机预防病毒感染有效的措施是______。
A.定期对计算机重新安装系统 B.经常重新启动计算机C.不准往计算机中拷贝软件 D.安装防病毒软件
参考答案:D
盒子内装有10张卡片,分别写有1~10的10个整数,从盒子中任取1张卡片,记下它的读数x,然后放回盒子内,第二次再从盒子中任取1张卡片,记下它的读数y.试求:(1)x+y是10的倍数的概率.(2)xy是3的倍数的概率.
— Is there _______ in today's newspaper?
— Yes. A group of ________ kids joined the volunteers!
A.anything new; ten-year-old
B.something new; ten-years-old
C.anything new; ten-years-old
D.something new; ten-year-old