**Explanation:**

In RCC beams, the neutral axis is defined as the line within the cross-section of the beam where the tensile and compressive stresses are equal. The depth of the neutral axis plays a crucial role in determining the behavior and strength of the beam.

When the percentage area of tensile steel in the beam increases, it means that more steel is added to resist the tensile forces. This has the following effects on the depth of the neutral axis:

**1. Increased Tensile Strength:**
- The addition of more steel increases the tensile strength of the beam. This means that the beam can resist higher tensile forces before failure.
- As a result, the neutral axis tends to move towards the tension side of the beam, away from the compression side.

**2. Increased Bending Moment Capacity:**
- The addition of more steel also increases the bending moment capacity of the beam.
- The bending moment capacity is directly related to the lever arm, which is the distance between the neutral axis and the extreme fiber of the beam.
- As the bending moment capacity increases, the lever arm also increases, causing the neutral axis to move towards the tension side of the beam.

**3. Redistribution of Stresses:**
- When the percentage area of tensile steel is increased, the steel absorbs a larger portion of the tensile stresses.
- This redistribution of stresses causes the neutral axis to move towards the tension side of the beam.

**4. Increase in Depth of Neutral Axis:**
- As a result of the above factors, the depth of the neutral axis increases when the percentage area of tensile steel in the beam increases.
- This means that the neutral axis moves away from the compression side and towards the tension side, resulting in a larger lever arm and increased bending moment capacity.

Therefore, the correct answer is option 'A', which states that the depth of the neutral axis increases as the percentage area of tensile steel increases in RCC beams.