Which statement is true regarding the relationship between vertebrates and chordates?
all chordates are vertebrates.
all vertebrates are chordates.
some vertebrates are chordates, and some are nonchordates.

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