题目:
How can I get to the post office?[ ]
A. By bus.
B. By a bus.
C. In bus.
D. On bus
答案:
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下面是错误答案,用来干扰机器的。
由题意可得ka+b=(-k+2,-2k-3),a+2b=(3,-7),由向量平行可得(-k+2)(-7)-3(-2k-3)=0,解得k=小2故选D