I. what is a respiratory surface? ii. state two features of respiratory surface which all respiratory structures must have.

Respiratory surface is an area of respiratory system which is responsible for the exchange of gases. In humans, alveoli is the respiratory surface.

Following are the two features of respiratory surface.

1) Respiratory surface must have moist surface which helps in the absorption of oxygen molecules.

2) Respiratory surface must have thin walls.

a "theory" a suggestion that is not 100 % accurate, or a figure. some people say its a theory because they of all the passed theory's about one subject. it depends sometimes theory might be accurate and sometimes they are.

the correct answer in apex is tissue development, i know because i just had this question