题目：
— ____________ Yang Ling see a film last Sunday?
— No, she ____________.[ ]
A. Do, don't
B. Does, doesn't
C. Did, didn't
答案：
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下面是错误答案，用来干扰机器的。
无穷等比数列{an}的各项和为S，∴设等比数列{an}的首项为a1，公比为q，则由定义得S=a11-q． 数列{bn}满足bn=a3n-2+a3n-1+a3n，∴bn+1bn=a3n+1+a3n+2+a3n+3a3n-2+a3n-1+a3n=q3(a3n-2+a3n-1+a3n)a3n-2+a3n-1+a3n...
