For active transport to occur, the following must be present.

Options

A. Carrier proteins, ATP, and cell membrane
B. Carrier proteins, ADP, and cell membrane
C. ATP, cell membrane, and vacuole
D. Cell membrane, water, and ATP

Explanation

To answer the question "For active transport to occur, the following must be present," we can break it down into a step-by-step explanation:

### Step-by-Step Solution:

1. **Definition of Active Transport**:
Active transport is the process by which cells move substances against their concentration gradient, meaning from an area of lower concentration to an area of higher concentration. This process requires energy.

2. **Energy Requirement**:
The first essential component for active transport is energy. This energy is typically derived from ATP (adenosine triphosphate), which is the energy currency of the cell. Without energy, the transport of molecules against their concentration gradient cannot occur.

3. **Carrier Proteins**:
The second requirement for active transport is the presence of specific proteins known as carrier proteins or transport proteins. These proteins facilitate the movement of substances across the cell membrane. They bind to the molecules that need to be transported and change shape to move them across the membrane.

4. **Cell Membrane**:
The third requirement is the cell membrane itself. The cell membrane is a semi-permeable barrier that separates the interior of the cell from the external environment. It is essential for active transport because it is the structure through which substances must pass.

### Summary of Requirements for Active Transport:
- **Energy (ATP)**
- **Carrier Proteins**
- **Cell Membrane**