How can you make the polymer stretch the farthest?

Two friends at different locations want to communicate with each other by sending low energy signals. which of the following methods can they use to communicate? a) produce x-rays using colliding electrons and send them to radios, which capture sound b) send messages using infrared radiation, which travel in the form of waves c) send radio waves through intervening media like radio and television d) produce sound waves using microwaves from heated objects

7. what temperature is need to just dissolve 50 g of nh4cl in 75 g of water? '

What can be found in the ionosphere