In a DNA Protection Assay Gel, Why Is It Necessary

In a DNA protection assay gel, why is it necessary to run sequencing ladders of the putative protein-binding DNA region along with DNase I-treated samples?

A) to establish the position of the binding protein relative to the transcription start site
B) to provide molecular weight markers
C) to check that the gel running conditions are correct
D) to check for nonspecific DNA degradation
E) none of the above