A boy run 5 km due west and then return back to travel a further distance of 4km before resting. the whole journey takes 1 hour calcute His total distance travelled
His average speed
his displacement from the starting point
his average velocity

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

the answer is the last option

explanation:

because in order to know what the molecule is you need to know how many atoms of each element are in the molecule.