Final answer:
Option (d), X-ray crystallography can determine the protein's tertiary structure, which is the three-dimensional arrangement critical to its function.
Step-by-step explanation:
For a protein that consists of a single subunit, X-ray crystallography can determine the protein's tertiary structure. The tertiary structure refers to the overall three-dimensional arrangement of a protein, which is critical for its function.
The sequence of amino acids, known as the primary structure, dictates the formation of secondary structures like alpha helices and beta sheets, which in turn fold into the unique tertiary structure. X-ray crystallography does not provide information on the genetic sequence encoding the protein (primary structure), the dissociation temperature, or the quaternary structure, as quaternary structure involves the arrangement of multiple subunits.