A:④-塔里木盆地
B:②-长江中下游平原
C:③-黄土高原
D:①-青藏高原
A traffic accident happened this morning. ____ (luck), no one was badly hurt.
在区间﹣2,3上任取一个数a,则函数f(x)=13x3﹣ax2+(a+2)x有极值的概率为____