The traditional approach __________with complex problems is to break them down into smaller, more easily managed problems.A. to dealingB. in dealingC. dealingD. to deal

步骤 1：理解句子结构
句子的主干是"The traditional approach is to break them down into smaller, more easily managed problems."，其中"to break them down into smaller, more easily managed problems"是动词不定式短语，作表语。
步骤 2：分析空格处的语法功能
空格处需要一个介词短语来修饰"the traditional approach"，表示"处理复杂问题的传统方法"。
步骤 3：选择正确的介词短语
选项A "to dealing" 中的"to"是介词，"dealing"是动名词，构成介词短语，符合语法要求。
选项B "in dealing" 中的"in"是介词，"dealing"是动名词，构成介词短语，但不符合句子的语义。
选项C "dealing" 是动名词，不能单独作为介词短语。
选项D "to deal" 中的"to"是不定式符号，"deal"是动词原形，构成不定式短语，不符合语法要求。