The computer system________suddenly while he was searching for information on the Internet.
A:broke up
B:broke away
C:broke out
D:broke down
在区间﹣1,1上随机取一个数k,使直线y=k(x+3)与圆x2+y2=1相交的概率为( )
In my eyes, my parents are the ____(严格的)in the world.
被称为“骑在羊背上的国家”和“坐在矿车上的国家”是( )
下列不属于对种群特征描述的是 ( )