This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nuclear medicine, Subject name: Radiology
Conversion of one nucleus into another was first demonstrated in 1919 by __________. 
Select and explain. 
A. Rutherford, B. Curie, C. Henry bequral, D. Roentgen
A: Rutherford
Answer: A: Rutherford 
Explanation: Ernest Rutherford is known as the father of nuclear physics. He discovered the concept of radioactive half-life, proved that radioactivity involved the transmutation of one chemical element to another, and also differentiated and named alpha and beta radiation. Henri Becquerel - discoverer of radioactivity. Marie Curie discovered Radium and Polonium, Coined the term "radioactivity".