Final answer:
The distance between Nathan and Rukmani and Koil Street cannot be determined without further information.
Step-by-step explanation:
In the given question, the distance between Nathan and Rukmani and Koil Street, where they think their son lives, is not provided. Therefore, it is not possible to determine the exact distance they are from Koil Street.
Without knowing the distance, it is not possible to select a specific option (a, b, c, or d) as the correct answer.
It is important to have all the necessary information to solve a problem or answer a question.