The best answer is B (semi permeable) The cell membrane of a red blood cell is semi permeable membrane. This is a type of biological membrane that will allow certain molecules or ions to pass through while barring others.
Red blood cells have very thin membranes that allow oxygen diffuse through quickly. They are also permeable to water and osmosis across the membrane occurs very rapidly. In the body, they are bathed in isotonic plasma in which case water movement into the cell is equal to water movement out of the cell and so the cells remain intact.
But we've never been to the planet's core. We haven't even come close. The central point of the Earth is over 6,000km down, and even the outermost part of the core is nearly 3,000 km below our feet.Aug 13, 2015
