Which of the following is true about density? it changes constantly
it cannot be used to identify a substance
it stays the same no matter how much of the substance that you have
it changes depending on how much of the substance that you have

italy's population growth rate is almost at zero, the national statistics agency, istat, said on monday, mainly due to a dwindling birth rate.

lunar landing mission. apollo 11 was the first manned mission to land on the moon. the first steps by humans on another planetary body were taken by neil armstrong and buzz aldrin on july 20, 1969. the astronauts also returned to earth the first samples from another planetary body.

explanation:

hydrogen is a compound or a single element and a element is a pure substence that cannot be separated into simpler subtances

clorine is a compound its a chemical substance that forms when two or more different elements combine

so both hydrogen and clorine are compounds