Simple diffusion and facilitated diffusion are two kinds of passive transport, which means they both have the following characteristics:
• Molecules move ,following the concentration gradient, (,high, concentration ,to low, concentration)
,
• Energy is not needed, for them to happen.
The main difference between them is that facilitated diffusion uses transport proteins, while simple diffusion doesn't.
This means A) both go with the concentration gradient (high to low) is the right answer.