Someone who inconspicuously harbors a pathogen and spreads it to others is a:

• A. carrier
• B. vector
• C. reservoir
• D. index case

Answer: (A)

Verified step by step guidance

1. Understand the definitions of each term: A 'carrier' is an individual who harbors a pathogen without showing symptoms and can transmit it to others; a 'vector' is an organism, often an insect, that transmits a pathogen between hosts; a 'reservoir' is a habitat or population where the pathogen normally lives and multiplies; the 'index case' is the first identified case in an outbreak.
2. Identify the key phrase in the question: 'inconspicuously harbors a pathogen and spreads it to others' implies the person does not show symptoms but can still transmit the disease.
3. Match the key phrase to the definitions: Since the individual is asymptomatic but can spread the pathogen, this fits the definition of a 'carrier'.
4. Exclude other options: A 'vector' is typically not a human but an organism like a mosquito; a 'reservoir' refers to a place or population, not an individual; the 'index case' is the first case identified, not necessarily asymptomatic or inconspicuous.
5. Conclude that the correct term for someone who inconspicuously harbors and spreads a pathogen is 'carrier'.