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 war.
A. basic
B. solid
C. unique
D. slide
网友回答
A. basic
(答案→)B. solid
C. unique
D. slide
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。