统计学常将P≤0.05或P≤0.01的事件称()
A.必然事件
B.不可能事件
C.随机事件
D.小概率事件
E.偶然事件
参考答案:D
“a的3倍与12的差是一个非负数”用不等式表示为______.
Many people in the West make ________ a rule to buy Christmas presents for their relatives and friends.[ ]
A.this
B.that
C.it
D.them