How do you overcome or reduce the problem of random error and systematic error while doing experiment

Long term exposure to waves can cause sunburns and skin cancer. a) visible b) infrared c) gamma rays d) ultraviole

Silver tarnishes as silver metal reacts with hydrogen sulfide, h2s, in the air. in this reaction, dark silver sulfide, au2s, covers the surface of silver. when silver is polished, this coating of silver sulfide can be removed from the surface. this makes the silver shiny again. enter the coefficients that balance the tarnishing reaction equation. (type 1 for no coefficient.)

How are isotopes of the same chemical element alike? how are they different?