The correct response to the question about the limitations of scientific models is:
They are too simple to represent complex phenomena.
This option highlights the fact that while scientific models aim to simplify and explain complex systems, they may not capture all the nuances and complexities of those systems. The other options are incorrect as they either misrepresent the nature of scientific models (e.g., claiming they are always 100% accurate or cannot be modified) or mischaracterize their application (e.g., stating they are only used in theoretical research).