Verbal Reasoning — Classification (Always/essential component): A “disease” always has what? Differentiate essential properties (must be true by definition) from typical but non-universal features such as germs or cures. Choose the necessary element.

Concept/Approach
By definition, a disease is a pathological condition that arises due to some cause (infection, deficiency, genetic factor, etc.). Not all diseases have a known cure; not all are caused by germs; and “patient” refers to the host entity but the essential logical property is causation.

Option Analysis

• Cure — many diseases have no cure.
• Germs — deficiency/autoimmune/genetic diseases lack germs.
• Cause — necessary (even if unknown to us, it exists). Correct.
• Patient — refers to a host, but the definitional requirement across contexts is causation.

Final Answer
Cause.