Filtration of wastewater flowing over a surface of land with vegetation and water is a O an artificial wetland
O a stabilization pond O
O a biodegradable treatment
O an open aeration pond

a- all cells come from pre-existing cells

the solute can move "downhill," from regions of higher to lower concentration, relying on the specificity of the protein carrier to pass through the membrane. this process is called passive transport or facilitated diffusion, and does not require energy.