Answer:
A
Explanation:
eons are divided into eras and eras are based on major events and can vary in time so eons can vary in time
Because despite being natural they still harm the ozone layer and cause breathing problems, even suffocation.
Answer:
3.01×10²³ atoms of calcium
Explanation:
number of moles = number of atoms/Avogadro's constant
n = N/NA
N = n×NA = 0.500 mol×6.02×10²³ mol^-1
N = 3.01×10²³ atoms of calcium