**Core Concept**
The question is testing the concept of aerosol deposition in the lungs, specifically the relationship between particle size and the ability to reach the alveoli. The alveoli are the smallest functional units of the lung where gas exchange occurs. For particles to reach the alveoli, they must be small enough to be inhaled deep into the lungs.

**Why the Correct Answer is Right**
Particles with a diameter of 1-5 micrometers (μm) can easily reach the alveoli due to their small size. This size range allows them to remain suspended in the air for a longer period, increasing the likelihood of inhalation. Additionally, the smaller particles can follow the airflow into the alveolar ducts and sacs, making them available for gas exchange. The **Mucociliary escalator**, a critical defense mechanism in the respiratory tract, is also less effective against these small particles, allowing them to penetrate deeper into the lungs.

**Why Each Wrong Option is Incorrect**
* **Option A:** Particles larger than 5 μm are unlikely to reach the alveoli, as they tend to be deposited in the upper airways, such as the trachea and bronchi, due to their larger size.
* **Option B:** Particles smaller than 1 μm may be exhaled without being deposited in the lungs, as they can pass through the airways without being retained.
* **Option D:** Particles larger than 10 μm are generally not inhaled, as they are too large to be carried by the airflow into the lungs.

**Clinical Pearl / High-Yield Fact**
The size of aerosol particles determines their deposition in the lungs, with particles between 1-5 μm being most likely to reach the alveoli. This concept is crucial for understanding respiratory diseases and the effectiveness of aerosolized medications.

**Correct Answer:** C.