Final answer:
The Intelligent Design Theory's key flaw is in its failure to account for genetic variation, which is essential for natural selection and the theory of evolution, and it's inadequately explained by the processes of mutation and diversification of DNA. So the correct answer is D.
Step-by-step explanation:
A key flaw of Intelligent Design Theory is that it fails to recognize the importance of genetic variation. This is critical because genetic variation is one of the fundamental mechanisms that drive the process of natural selection, which is central to the theory of evolution. Genetic variation results from random mutations in DNA, which then leads to different traits or characteristics, some of which give certain individuals an advantage in survival and reproduction in particular environments. Darwin's theory of evolution through natural selection depends on this genetic variation to explain the diversity and complexity of life forms that we see today.
The Intelligent Design Theory suggests that certain complex biological features cannot be fully explained by natural processes like natural selection and instead require an intelligent force behind their existence. However, by not adequately accounting for the role of genetic variation and how it can lead to complex organisms without the need for an intelligent designer, the theory is seen by many in the scientific community as lacking explanatory power in the face of well-supported evolutionary processes documented by biology.