Which best describes what is required for any sound wave to travel?

Plss anybody know how to do this? ? i need the answers from a through d

Along the line connecting the two charges, at what distance from the charge q1 is the total electric field from the two charges zero? express your answer in terms of some or all of the variables s, q1, q2 and k =14ï€ïµ0. if your answer is difficult to enter, consider simplifying it, as it can be made relatively simple with some work.

Achlorine atom has 17 protons and 18 neutrons. what is its mass number? what is its atomic number?