You multiply 6.50 by the molar mass of H2SO4.
C=0.10 mol/l
pH=-lg[H⁺]
HCl = H⁺ + Cl⁻
pH=-lgc
pH=-lg0.10=1.0
pH=1.0
In living things, the source of the carbon-14 that is used in radiocarbon dating is carbon dioxide in the atmosphere.
Living things inhale oxygen, and exhale carbon dioxide into the atmosphere, which is why the air and atmosphere are so full of it.
I believe the answer is C