Shared feature of facilitated diffusion and active transport

Steps:

• Recall facilitated diffusion: passive movement of specific molecules down concentration gradient via channel or carrier proteins.
• Recall active transport: energy-requiring movement of specific molecules against concentration gradient via carrier proteins.
• Identify common trait: both rely on membrane proteins selective for particular molecules.
• Evaluate options: select statement true for both processes.

Why C is correct:

• Both processes use specialized carrier or channel proteins that transport only specific molecules, as defined by selective permeability in cell membrane transport.

Why the others are wrong:

• A: Active transport moves molecules against the gradient regardless of its direction, unlike facilitated diffusion.
• B: Incomplete; transport occurs via proteins, not "always" without specificity or mechanism.
• D: ATP is required only for active transport, not for passive facilitated diffusion.

Final answer: C