Final answer:
The landmark Report on the Sanitary Commission of Massachusetts, which stimulated public health reform in the United States, was written by Lemuel Shattuck. Therefore, the correct option is D. Lemuel Shattuck.
Step-by-step explanation:
The landmark Report on the Sanitary Commission of Massachusetts, which stimulated public health reform in the United States, was written by Lemuel Shattuck. The report was published in 1850 and provided comprehensive recommendations for improving public health and sanitation measures in Massachusetts.