I will mark brainliest I kind of want the math explanation to go with it if at all possible, as I am struggling

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

Is a pencil falling to the floor anon contact force, a force, or a contact force

Which of these features are formed when hot groundwater is forced out through cracks in the earth's surface?