Which would show an example of how physical changes are reversible? cutting a gold bar in two pieces and then putting the pieces next to each other
burning a match and then relighting it
melting tin and then cooling it into a mold
combining sodium and chlorine to make the new material of table salt

C

Explanation:

the physical change was the gold bar being cut and if it is put back together the physical change is reversed

one "light year" is the distance that light travels, through vacuum, in one julian year.   that's 365.25 days, of 24 hours each.

third one with arrows on top of each other going the same direction