Q:

IUPAC Nomenclature for aldehyde

I was trying to name the following compound and I thought that if both the aldehyde group carbons should be included in the parent chain or I should go with the longest chain .  I saw the solution for this and got two answers as I) 3-(Formylmethyl)hexanal and 2) 3-Propylpentanedial.  
Can someone please help me in naming it correctly?? 

A:

IUPAC (2013) rule

P-44.1.1 The senior parent structure has the maximum number
  of substituents corresponding to the principal characteristic
  group (suffix) or senior parent hydride …

(more e.g. here) is applied in the phase of selecting "parent structure", before than the "longest chain rule" (P-44.3.2, e.g. here) in the phase of selecting the "principal chain". 
Therfore the latter name, 3-propylpentanedial, is correct.