Movement into and out of cells — practice question

Which statement gives the correct description of facilitated diffusion?

• AThe process only occurs using channel proteins that change shape and that use energy provided by the cell.
• BThe process occurs using channel proteins or carrier proteins that may or may not change shape.
• CThe process occurs using channel proteins or carrier proteins that use energy provided by the cell.
• DThe process only occurs using carrier proteins that create a gradient to move ions in opposite directions.