What organism is primarily responsible for nitrogen fixation

Which muscle is responsible for inhalation ?

The current thought on the structure of the cell membrane is: a. a static phosphate sandwich of lipids b. a fluid-mosaic of phospholipids and proteins c. a bilayer of proteins with static lipid molecules d. an impermeable bilayer of protein molecules e. a static and permeable phospholipid single layer

What materials must dams have to produce electricity, and what must occur?