Final answer:
Particles between 1-5 mcm in size primarily affect the bronchioles of the respiratory system. These particles can evade the initial filtering in the nasal cavity and are small enough to reach the smaller airways.
Step-by-step explanation:
Particles between 1-5 micrometers (mcm) in size can affect different parts of the respiratory system. When air enters the respiratory system through the nasal cavity, mucus and hairs trap larger particles. As air continues down the respiratory tract, it passes through the larynx, trachea, bronchi, and bronchioles before reaching the alveoli. Smaller particles in the 1-5 mcm range have the potential to evade the initial filtering mechanisms of the nasal cavity and reach the smaller airways like the bronchioles and the alveoli.
Considering the size of the particles in question and the structure of the respiratory system, the most likely answer to the student's question is:
b) Bronchioles
Particles this small are not typically trapped in the larger airways like the nasal cavity or trachea and can reach the smaller bronchioles, potentially causing irritation or damage. The bronchioles then lead to the alveoli, where gas exchange occurs, and these smaller particles could potentially reach and affect the alveoli as well. However, the primary point of impact for particles of 1-5 mcm would be the bronchioles.