Which of the following are NOT the parts of the exchange part of the respiratory system of human beings?
A. Trachea 
B. Alveolar ducts
C. Primary bronchi
D. Secondary bronchioles
E. Alveoli
Choose the correct answer from the options given below.

- Trachea (A) is not part of the exchange part; it is part of the conducting part of the respiratory system.
- Primary bronchi (C) are also part of the conducting part, not the exchange part.
- Secondary bronchioles (D) are part of the conducting part as well, not the exchange part.
Alveolar ducts and alveoli are parts of exchange zone where exchange of oxygen and carbon dioxide occurs.