(IP 
  (ADVP 
    (AD 而))
                    
  (NP-SBJ 
    (ADJP 
      (JJ 一般))
                    
    (NP 
      (NN 卖场)))
                    
  (VP 
    (DP-ADV 
      (DT 每)
                    
      (CLP 
        (M 天)))
                    
    (VP 
      (VV 可能)
                    
      (VP 
        (VV 需要)
                    
        (NP-OBJ 
          (QP 
            (CD 二十))
                    
          (NP 
            (NN 人)))
                    
        (IP 
          (NP-SBJ 
            (-NONE- *PRO*))
                    
          (VP 
            (VV 清扫)
                    
            (NP-EXT 
              (QP 
                (CD 数))
                    
              (NP 
                (NN 小时)))))))))
arg0: 
                    *PRO* 
                
argm: 
                    数 小时