What does standard deviation reveal about data

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

At stp, what is the volume of 1 mole of co2?

If an area has high air pressure and low humidity, what type of weather will it most likely have? plz !