Which one of the following is the correct statement for respiration in humans?
1. | Cigarette smoking may lead to inflammation of the bronchi |
2. | Neural signals from the pneumotaxic centre in the pons region of the brain can increase the duration of inspiration |
3. | Workers in grinding and stone-breaking industries may suffer from lung fibrosis |
4. | About 90% of carbon dioxide (CO2) is carried by haemoglobin as carbaminohaemoglobin |