C. a toy train is the item that has characteristics similar to a scientific model.
<span>The quality of Australian land is unique as the properties of the earth crust are different. There is no much of evolution of land and is an isolated space which is the reason for the said placental mammals do not habitat there but has their own diverse kind of these marsupials.</span>
<span>The
answer is facilitated diffusion. It requires no energy because the ions are
traveling down the concentration
gradient. Facilitated diffusion is important
for the regulation of ions in a cell. It also enables
ions to pass across the hydrophobic layer of the cell membrane composed
of phospholipids.</span>
