Four administrators (A, B, C, and D) from a company have written letters about four topics: Energy, Security, Nutrition, and Manpower. Each letter has a unique topic, sender, and receiver.
- the admin who has sent a letter about nutrition has received a letter about security from A.
- the letter which has been sent by B has been received not by D.
- the letter which has been received by D wasn't about nutrition.
- none of the two admins have written letters to each other (for example, we don't have "B to A" if we have "A to B").
Question: If the letter about manpower has been sent by D, which admin has received the letter about energy?