What is the percent composition of each element in the compound below? MgCO3 (answer to the nearest 0.1%)
Mg- ___%
C- ___%
O- ___%

The answer for #3 is c but i don't know why

One way that radioactive waste is treated is by burying it in repositories. the repositories are found only in states with very low populations. true or false? a. trueb. false(also i meant to put high school but it put down middle school instead)

8.98 dm3 of hydrogen gas is collected at 38.8 °c. find the volume the gas will occupy at -39.9 °c if the pressure remains constant.