Dr. Bob hypothesizes that drug X causes cuts to heal more quickly. He performs a medical experiment on a group of 100 people and confirms his original hypothesis. In the control group, a 1 cm cut took seven days to heal. In the experimental group, a 1 cm cut took four days to heal. What should Dr. Bob do next?
A) Repeat the experiment for accuracy.
B) Begin selling drug X to the public.
C) Write a scientific theory about drug X.
D) Publish the results of the experiment in a scientific journal.