Coolest doubt in Mahabharata

In some remote village of India, one masterji is teaching theMahabharataStory to class 6 students.He is at the 'Krishna janma' part of it. Masterji: "Kamsa heard the Aakaashwani that his sister's 8th child isgoing to kill him.He was furious. He ordered to put vasudev n devki behind the bars. First Son is born, and kamsa kills him by poisoning... Second one is born n kamsa throws him off the mountain peak. Third one is born ...... Now JS, who is smartest of the lot, puts up his hand. "Masterji, I have a doubt" (sounding nervous n confused) Masterji: "JS beta, whole India does not have doubt in Mahabharata Then how come u have one?" JS: "Masterji, if Kamsa knew that Devaki's 8th child was going to kill him, WHY THE HELL DID HE PUT VASUDEV AND DEVAKI IN THE SAME CELL? " Masterji fainted..... ......... ......... ...