The respiratory system includes a layer of cells in the air passages that clean the air before it gets to the lungs. this layer of cells is best classified as ) an organ system(2) an organ (3) an organelle(4) a tissue

4) a tissue

Explanation:

When a group of cells come together to perform a specified function, they are referred to as tissue. When a group of tissues come together to perform a specified function, they become an organ. If a group of organs, come together to perform a specific function, they are referred to as a System.

the cladogram shown here shows similarities and differences among several classes of vertebrates. anatomically, the four have limb structure as their common ancestor. we might separate the mammals from the other three classes because they a) divergent; do not lay eggs b) identical; are warm-blooded c) varied; a four chambered heart d) homologous; have mammary glands