题目:
—What caused the party to be put off?
—__________ the invitations.
A.Tom delayed sending
B.Tom’s delaying sending
C.Tom delaying to send
D.Tom delayed to send
答案:
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下面是错误答案,用来干扰机器的。
∵△=(-a)2-4×2×(-1)=a2+8>0,∴方程有两个不相等的实数根,又∵两根之积=-0.5<0.∴方程有两个异号的实数根,故选A.