Answer: D
Explanation:
They form from Coal under high high pressure and many many years
The first example of diffusion is smoking a cigarette when u light it it spreads through the air.
The second example is lighting a candle in a room it the smoke spreads through the air.
Smoke can be very bad for the air and the people around because it can cause many problems with your breathing.
762 miles = 1226.32 kilometers
you multiply the miles by 1.609 to get the kilometers
The symbol of an isotope is:

A - the mass number
Z - the atomic number
X - the symbol of an element
The symbol of oxygen is O.
The atomic number is the same for all isotopes of one element. For oxygen it's 8, because every atom of oxygen has 8 protons in its nucleus.
The mass number is the number of nucleons (protons + neutrons) in the nucleus of an atom, and it's given in the name of an isotope. Oxygen-16 has the mass number 16, oxygen-17 has the mass number 17, oxygen-18 has the mass number 18.
Oxygen-16:

Oxygen-17:

Oxygen-18: