Risha runs to the North of her place and stay at point A after travelling 25 km and she finds that she has run in the wrong direction. She then turns to her right and runs 21 km, and then she again turns to the right and runs straight another 25 km. How much distance has she now to cover to go back to the starting point?

• A. 21 km
• B. 25 km
• C. 40 km
• D. 4 km