Why isn't energy ever truly destroyed?

Who is better, messi or cristiano, i need this for a chemistry class. asap

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

Which step in naming unsaturated hydrocarbons is used for alkenes but not alkynes