Answer:
C. He realized that no two people had the same fingerprint.
Step-by-step explanation:
William Herschel was a civil servant, who worked for the British civil administration in Calcutta. Its function was to pay Indian employees. This was a very difficult function for Herschel. That's because he had to organize the payment of many people who were very similar to him. He could not recognize them either by appearance or by name, as they were very different names for him.
That's when he realized that one person's fingerprint is not the same as another person's fingerprint. Therefore, he decided to archive the fingerprint of all employees. Thus, every time an employee received his payment, he had to sign a document and leave the fingerprint mark on his index and middle fingers, to be compared to the stored fingerprint.