Answer:
C
Step-by-step explanation:
The number of particles of any kind in 1 mol is 6.02*10^23.
How you modify that depends on the units.
The number of molecules in 1 mole of hydrogen is 6.02*10^23 molecules.
Each molecule consists of 2 atoms. Pure hydrogen at STP will have a multiplier of 2.
So the number of atoms is 2*6.02 * 10^23 = 1.20 * 10^24 atoms.