In which of the following are the symbol and name for the ion given correctly?
a) Fe^2+: ferrous ion; Fe^3+: ferric ion
b) Sn^2+: stannic ion; Sn^4+: stannous ion
c) Co^2+: cobalt (II) ion; Co^3+: cobaltous ion
d) Pb^2+: lead ion; Pb^4+: lead(IV) ion