(IP-OBJ 
  (IP-SBJ 
    (NP-SBJ 
      (PU 「)
                    
      (NN 中年)
                    
      (NN 危机)
                    
      (PU 」))
                    
    (VP 
      (PP-LOC 
        (P 在)
                    
        (NP-PN 
          (NR 美国)))
                    
      (VP 
        (VV 形成)
                    
        (NP-OBJ 
          (ADJP 
            (JJ 热门))
                    
          (NP 
            (NN 议题))))))
                    
  (PU ，)
                    
  (VP 
    (IP-ADV 
      (NP-SBJ 
        (-NONE- *PRO*))
                    
      (VP 
        (VV 探究)
                    
        (NP-OBJ 
          (NN 原因))))
                    
    (PU ，)
                    
    (VP 
      (VC 是)
                    
      (IP-PRD 
        (LCP-TMP 
          (IP 
            (LCP-SBJ 
              (NP-APP 
                (NT 一九四六年))
                    
              (LCP 
                (IP 
                  (NP-SBJ 
                    (QP 
                      (OD 二)
                    
                      (CLP 
                        (M 次)))
                    
                    (NP 
                      (NN 大战)))
                    
                  (VP 
                    (VV 结束)))
                    
                (LC 後)))
                    
            (VP 
              (VV 以迄)
                    
              (NP-OBJ 
                (NT 一九六四年))))
                    
          (LC 间))
                    
        (PU ，)
                    
        (NP-SBJ 
          (CP 
            (WHNP-2 
              (-NONE- *OP*))
                    
            (CP 
              (IP 
                (NP-SBJ 
                  (-NONE- *T*-2))
                    
                (VP 
                  (VV 为数)
                    
                  (QP-OBJ 
                    (ADVP 
                      (AD 约))
                    
                    (QP 
                      (CD 七千五百万)))))
                    
              (DEC 的)))
                    
          (NP 
            (PU 「)
                    
            (NN 婴儿潮)
                    
            (PU 」)))
                    
        (VP 
          (ADVP 
            (AD 陆续))
                    
          (VP 
            (VV 出生)))))))
arg0: 
                    *PRO* 
                
arg1: 
                    原因