Final answer:
The word 'neurological' is associated with diseases of the nervous system, which can be derived from the breakdown of the word 'neurotropic'. Neurological diseases include both neurodegenerative and neurodevelopmental disorders.
Step-by-step explanation:
If you break down the word "neurotropic" into root words, prefixes, and suffixes, the word associated with diseases of the nervous system would be "Neurological". The prefix 'neuro-' refers to the nerves or the nervous system, and the suffix '-logical' pertains to the study or science of a particular subject. Therefore, C. Neurological is the answer that is most closely related to diseases of the nervous system such as neurodegenerative diseases like Alzheimer's disease, Parkinson's disease, and multiple sclerosis (MS), or neurodevelopmental disorders like attention deficit hyperactivity disorder (ADHD), for which stimulants are often used as a treatment.