Which structure in these animals helps protect their internal body parts? shell backbone gills muscles

What is the following best defines climate?

Moving down the ramp from 6 meters to

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