An infectious disease is most accurately defined as:

• A. a disease caused by the invasion and multiplication of pathogenic microorganisms in the body
• B. any disease that is inherited genetically from parents
• C. a condition caused by an allergic reaction to environmental substances
• D. a non-communicable disease resulting from environmental factors

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the key terms in the question. 'Infectious disease' refers to diseases related to microorganisms such as bacteria, viruses, fungi, or parasites.
2. Step 2: Analyze each option by comparing it to the definition of infectious diseases. Infectious diseases involve invasion and multiplication of pathogenic microorganisms in the body.
3. Step 3: Recognize that diseases inherited genetically are classified as genetic or hereditary diseases, not infectious diseases.
4. Step 4: Identify that allergic reactions are immune responses to environmental substances and do not involve microorganisms, so they are not infectious diseases.
5. Step 5: Note that non-communicable diseases caused by environmental factors do not involve pathogens and are not infectious diseases.