B) Alveolar ventilation is less than pulmonary ventilation.

Explanation:
To understand the difference between pulmonary ventilation and alveolar ventilation, let's first define these terms:

- Pulmonary ventilation: It refers to the total volume of air that moves in and out of the lungs in a minute. It includes both the volume of fresh air reaching the alveoli (tidal volume) and the volume of air that remains in the conducting airways (anatomical dead space).

- Alveolar ventilation: It refers to the volume of fresh air reaching the alveoli per minute. It is the portion of pulmonary ventilation that participates in gas exchange with the blood.

Now, let's discuss why alveolar ventilation is less than pulmonary ventilation:

1. Anatomical dead space: The conducting airways, including the nasal passages, pharynx, trachea, bronchi, and bronchioles, do not participate in gas exchange. The air in these regions is referred to as anatomical dead space. During inhalation, a portion of the inspired air occupies this space and does not reach the alveoli. Therefore, the volume of air reaching the alveoli for gas exchange is less than the total pulmonary ventilation.

2. Tidal volume: Tidal volume is the volume of air inhaled and exhaled in a single breath. It includes both the volume that reaches the alveoli and the volume that fills the anatomical dead space. Since alveolar ventilation is the volume of fresh air reaching the alveoli per minute, it is dependent on the respiratory rate and the tidal volume. If the tidal volume is increased without a corresponding increase in the respiratory rate, a larger portion of the inspired air will fill the anatomical dead space, reducing the alveolar ventilation.

3. Physiological dead space: In addition to the anatomical dead space, there is also a physiological dead space caused by ventilation-perfusion mismatch in the lungs. This refers to the alveoli that are ventilated but not perfused by blood, leading to inefficient gas exchange. The physiological dead space further reduces the effective alveolar ventilation.

Therefore, alveolar ventilation is less than pulmonary ventilation because a portion of the inspired air occupies the anatomical dead space and does not participate in gas exchange, and there is also ventilation-perfusion mismatch in the lungs.