Sona's Movement:
- Sona initially walks 10 meters in front of her starting point.
- She then walks 10 meters to the right, which means she has moved 10 meters horizontally.
- From this new position, she starts turning left and walks 5 meters.
- After that, she turns left again and walks 15 meters.
- Finally, she turns left once more and walks 15 meters again.

Calculating the Distance:
To find out how far Sona is from her starting point, we can break down her movements into horizontal and vertical components.

Horizontal Distance:
- Sona initially moves 10 meters to the right, which adds to her horizontal displacement.
- Then, she walks 15 meters to the left, canceling out part of her horizontal displacement.
- Finally, she walks another 15 meters to the left, further canceling out her previous displacement.

Since her horizontal displacement was initially 10 meters and then canceled out by walking 15 meters to the left twice, her net horizontal displacement is 10 - 15 - 15 = -20 meters. The negative sign indicates that she is 20 meters to the left of her starting point.

Vertical Distance:
- Sona initially moves 10 meters in front, which adds to her vertical displacement.
- Then, she walks 5 meters to the left, which has no effect on her vertical displacement.
- Finally, she walks 15 meters to the left twice, which also has no effect on her vertical displacement.

Therefore, her net vertical displacement remains 10 meters.

Using the Pythagorean theorem, we can calculate the distance between her current position and the starting point using the horizontal and vertical displacements:

Distance = √(horizontal displacement)^2 + (vertical displacement)^2
Distance = √((-20)^2 + 10^2)
Distance = √(400 + 100)
Distance = √500
Distance ≈ 22.36 meters

So, Sona is approximately 22.36 meters away from her starting point. None of the given options (a, b, c, or d) match this distance, so none of them are the correct answer.