Why did Hershey and Chase label the viral DNA with radioactive phosphorous and not radioactive sulfur?

Well, all DNA contains phosphorus, and lacks sulfur, whereas protein contains sulfur but no phosphorus. Only one sample had only radioactive DNA while the other only contained radioactive protein.

sorry to break it to ya but no one can answer your question it's just

jk but i am serious about the part that most people cant answer it beacuse you did not mention the section you are talking about. but it would if you added some detail and were a bit more specific.