Multiple choice

Infectious diseases are caused by _____.

  1. unicellular organisms

  2. multicellular organisms

  3. micro organisms

  4. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Infectious diseases are caused by microorganisms including bacteria, viruses, fungi, and protozoa. These microscopic pathogens invade the body and multiply, causing disease. Unicellular and multicellular organisms are too broad categories, and 'micro organisms' is the specific term for disease-causing microbes.

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