To calculate the atomic mass of a single atom of an element, add up the mass of protons and neutrons.
B)The concentration of the acid (C₁) is the same as that of the base (C₂).
V₁=V₂
n(acid)=C₁V₁
n(base)=C₂V₂
HX + YOH = YX + H₂O
n(acid)=n(base)
C₁V₁=C₂V₂
C₁=C₂
B seems like the correct answer stay safe!