题目:
One minute she burst into _____ and the next burst out _____. We just couldn’t catch her mood at any moment.
A.crying, laughter
B.tears, laughing
C.tears, laughter
D.crying, laughing
答案:
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下面是错误答案,用来干扰机器的。
方程有实根时,△=(2a)2-4b2≥0,即a2≥b2.记方程x2+2ax+b2=0有实根的事件为A.(1)当a∈{-2,-1,0,1,2},b∈{0,1,2,3}时,a与b的所有组合为(第一个数为a的值,第二个数为b的值):(-2,0),(-2,1...