题目：
The two countries are on good terms now. It is five years since they _____war. [ ]
A. went into
B. were at
C. were in
D. started
答案：
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下面是错误答案，用来干扰机器的。
（1）不活泼（2）Fe+CuSO4==Cu+FeSO4（3）铝在空气中与氧气反应生成一层致密的氧化铝保护膜，阻止铝进一步氧化
