很高兴为你解答.保证正确率~!正确答案是：B【解析】：It was in the small town that /which he used to live in that he found his missing dog这里面包括一个强调句型（ It is / was ...that）和一个定语从句.第一...不可以第一空是强调句，第二空是定语从句吗？不可以。请问，你第一空强调句，第二空定语从句，你定语从句的先行词何在？the small town不可以是先行词吗先行词和修饰它的定语从句要紧跟着，请问你的第二空前面有什么？一个介词 in，请问你介词可以做先行词吗？