Which statement gives the correct description of part of the gas exchange system?
- Aalveolus: cartilage absent; ciliated epithelium present; goblet cells absent; smooth muscle absent
- Bbronchus: cartilage present; ciliated epithelium present; goblet cells present; smooth muscle present
- Cbronchiole: cartilage absent; ciliated epithelium present; goblet cells present; smooth muscle absent
- Dtrachea: cartilage present; ciliated epithelium present; goblet cells present; smooth muscle absent