The four important characteristics of respiratory surface are:
1. Thin walls
2. Moisture
3. Large surface area
4. Blood supply
Respiratory system or respiratory tract is divided into upper and lower tract. Upper respiratory tract includes nose and its cavities, sinuses, pharynx and the part of the larynx. Lower respiratory tract consists of the trachea, bronchi, bronchioles and the alveoli.
Alveoli are the ends of the respiratory tract the smallest units in it. Alveoli are small folded air sacs that are branching off from alveolar ducts and providing an extremely large surface area for the gas exchange. Gas exchange occurs thanks to small blood vessels – capillaries that surround alveoli and it occurs via the process of diffusion.
So, respiratory surface is thin membrane also known as the blood–air barrier that consists of the alveolar epithelial cells, their basement membranes and the endothelial cells of the alveolar capillaries.
Answer:
• An acid is an electrolyte that hydrolyses in water to release hydrogen ions.

• pH level of an acid;
- Strong acid → 0 - 3.8
- Weak Acid → 4.0 - 6.7
Answer:
well i belive its growth hope that helps
Its often referred to as the colon
<span>The best place would be far away from a cliff and the worst would be right on top of a cliff or some sort of land such as a beach or directly beneath it. At anytime, gravity will cause mass wasting, in other words the rock and soil will just break apart.</span>