Which organ allows the exchange of oxygen and carbon dioxide?​

Respiratory System

convex lenses are thicker at the middle. rays of light that pass through the lens are brought closer together (they converge). a convex lens is a converging lens. when parallel rays of light pass through a convex lens the refracted rays converge at one point called the principal focus.

are there answer choices to this question? this seems like a question where you have options to choose from.