**Explanation:**

In the story "The Lost Child" by Mulk Raj Anand, Sergei is a lost child who wanders away from his parents in a fair. He gets separated from them and starts feeling scared and anxious. However, he is eventually set on the right path by Olga, a kind and compassionate girl.

**Olga's Role:**

Olga plays a crucial role in helping Sergei find his way back to his parents. Here's an explanation of why option 'D' - Olga is the correct answer:

1. **Compassionate and Caring:** Olga is portrayed as a kind-hearted and caring girl in the story. When she sees Sergei lost and crying, she empathizes with him and takes it upon herself to help him. This compassion and care for a stranger in need set her apart and make her the guiding force for Sergei.

2. **Leadership and Initiative:** Olga takes the lead in the situation and decides to help Sergei. She guides him, holds his hand, and walks with him through the crowd, ensuring his safety. Her initiative and leadership are vital in setting Sergei on the right path and helping him overcome his fear and confusion.

3. **Reassurance and Support:** As they walk together, Olga provides reassurance to Sergei, calming his anxieties. She tells him that they will find his parents and assures him that everything will be alright. This support and encouragement give Sergei the confidence he needs to trust Olga and follow her lead.

4. **Empathy and Understanding:** Olga understands Sergei's fear and confusion as she puts herself in his shoes. She remembers her own experience of getting lost in the fair as a child and empathizes with Sergei. This understanding allows her to connect with Sergei on an emotional level and offer the help he needs.

5. **Successful Reunion:** Ultimately, Olga's efforts bear fruit as she successfully reunites Sergei with his parents. She takes him to the police station, where Sergei's parents are waiting anxiously. This highlights her effectiveness in setting Sergei on the right path and ensuring his safe return.

In conclusion, Olga's compassionate nature, leadership, reassurance, empathy, and successful reunion with Sergei's parents make her the person who sets Sergei on the right path in "The Lost Child."

From past many years, Sergei was in Pride that he set a drunkard on a right path. But later on, when Lushkoff revealed that Olga has saved him, then his Pride has shattered and he knew the reality.