Nothing can separate the two, because they have a friendship foundation dating back to their childhood when they had to depend on each other to survive in the warA.basicB.solidC.uniqueD.slide
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B解析考查形容词的用法：A. basic基础的，B. solid牢固的，C. unique独特的，D. slide滑落；下跌，句意是：没有什么可以分开两个人，因为他们有牢固的友谊基础，可以追溯到童年时期，那时他们要彼此依赖在战争中幸存。选B。