The cell membrane is selectively permeable, allowing only certain substances to pass through. Passive transport is a way that small molecules or ions move across the cell membrane without input of energy by the cell. The three main kinds of passive transport are diffusion, osmosis, and facilitated diffusion.
Mercury, Venus, Earth, and Mars are all known as terrestrial planets I believe.
Flatworm get most of their oxygen through diffusion.
I believe the answer is (B)
<span>a complex series of feeding relationships with many organisms interacting and depending on each other </span>
