Which describes a difference between birds and mammals? Birds protect and feed their young.
Birds have nearly hollow bones.
Birds undergo internal fertilization.
Birds efficiently transport oxygen to cells.

✿   this landform has a high elevation and a high relief

✿   this landform is a mountain

the answer is z.

the human body has five levels of organization. level 1: cells. cells are the basic units of life and form the first level of organization. cells in the human body have specific functions. examples include nerve cells, blood cells, liver cells, and so on.

(nitrogen fixation) will be your answer sorry if im wrong