(a)[4]
Complete the table to show how the structural features are distributed in the parts of the gas exchange system, A to D, shown in Fig. 5.1. Put a tick (✓) if a feature is present and a cross (\times) if it is absent. Some boxes have already been filled in for you.
(b)[4]
Explain the role of goblet cells and cilia in maintaining a healthy gas exchange system. Goblet cells: explain their function. Cilia: explain their function.