The only pair of quadratic functions whose graphs satisfy the condition are q(x) = 
 - 18 and w(x) = 
 and the correct option is D.
Since the vertex of the graph of q is 18 units below the vertex of the graph of w, this means that the y-value of q(x) is always 18 less than the y-value of w(x) for any given x-value.
Option A, q(x) = 18
 and w(x) = 
, does not satisfy this condition because the difference in their y-values is not always 18.
Option B, q(x) = 
 + 18 and w(x) = 
, also does not satisfy the condition because the difference in their y-values is always 18, which means their graphs would coincide.
Option C, q(x) = -18
 and w(x) = 
, does not satisfy the condition because the vertex of the graph of q would be 18 units above the vertex of the graph of w, not 18 units below.
Option D, q(x) = 
 - 18 and w(x) = 
, satisfies the condition because the difference in their y-values is always 18. This means that the vertex of the graph of q is 18 units below the vertex of the graph of w.
Therefore, the pair of functions that could have been used to create the graphs of q and w is q(x) = 
 - 18 and w(x) = 
 and the correct option is D.