Answer:
It means that the cell membrane allows certain substances to pass through and not others. As the cell membrane consists of a phospholipid bilayer with a hydrophobic core, only small uncharged hydrophobic molecules can pass through the cell membrane e.g. glucocorticoid and other larger charged particles require transporters or channel proteins to pass through the cell membrane, e.g. glucose.
The aortic valve prevents backward flow of blood into the left ventricle.
Metaphase is when the spindles attach to the chromosomes and they move to the center.
Plantae is the correct answer
