Given f(w, x, y, z) = Σm(0,1,2,3,7,8,10) + Σd(5,6,11,15), where d represents the don’t-care condition in Karnaugh maps. Which of the following is a minimum product-of-sums(POS) form of f(w,x,y,z)?
a: f = (w' + z' )( x' + z )
B: f = (w' + z ) ( x + z )
C: f = ( w + z ) ( x ' + z )
D: f = ( w + z' ) ( x' + z )