Answer:
b. octadecanoic acid
Explanation:
For explanation please see the attached file.
Mass number = protons + neutrons. 12 + 11 = 23.
Potassium (K), Sodium(Na), Iron(Fe), Copper(Cu), Silver(Ag), Tin(Sn), Antimony(Sb), Tungsten(W), Gold(Au), Mercury(Hg), Lead(Pb)