**Core Concept**
The process of transporting substances across cell membranes requires energy to maintain the concentration gradient. This is achieved through the use of ATP, which is generated by cellular respiration. The process being tested is an example of a secondary active transport mechanism.

**Why the Correct Answer is Right**
The correct process is facilitated diffusion, which is a type of passive transport that moves substances down their concentration gradient without the need for energy. This process does not require ATP, and it occurs through the use of carrier proteins or channels. However, if the process requires energy to move against the concentration gradient, it would be an example of active transport. In this case, the correct answer is not one of the options listed, but rather **Option A:** is actually the correct process that requires energy - Active transport.

**Why Each Wrong Option is Incorrect**
**Option A:** is actually the correct process that requires energy - Active transport. This is because active transport involves moving substances against their concentration gradient, which requires energy in the form of ATP.
**Option B:** (Facilitated diffusion) is incorrect because it does not require energy to move substances down their concentration gradient.
**Option C:** (Simple diffusion) is incorrect because it does not require energy to move substances down their concentration gradient.
**Option D:** (Osmosis) is incorrect because it is a type of passive transport that moves water molecules down their concentration gradient, and does not require energy.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that active transport requires energy in the form of ATP to move substances against their concentration gradient, whereas passive transport does not require energy to move substances down their concentration gradient.

**Correct Answer:** A. Active transport.