How many layers is earth made out of?

Is the best definition of half-life for a radioactive substance A. Half of the amount of time required for all of the radioactive atoms to decay. B. The amount of time required for half of the rad? What is the element with charge if needed with 23 protons 28 neutrons and 18 electrons with a net charge of 3 plus? How many pints fit in a liter? What experimental technique would you use choose a suitable solvent? What crosses would give 100 of the purple flowers phenotype but also would allow you to set the white flower phenotype in the following generation? The interstellar medium is approximately 99 percent gas and 1 percent dust Why is it the dust and not the gas that blocks your visible-light view of the galactic center? How long would it take a man to run 500metres in 10metres per second? What rock is made up of the smallest sediminate? Ribosomes receive directions from hereditary material to make certain what? How does the water cycle work? What is stress pulling outward? What is the Structural formula of 4-ethyl-234-trimethyloctane? How many feet would a ton of limestone cover 4 inches deep and 8 feet wide? How are insects related to landslide hazards? What types of impurities does the Maytag UKF7003AXX PuriClean water filter remove? Where does tulip belongs aerial terrestrial or water plants? What is long form of UDCT? Under what circumstances do the colliding molecules not react? Where can metamorphic rock be found? Which fusion reaction could possibly result in fusion being a viable source of energy dt reaction dd reaction or protium reaction?