Final answer:
The correct names and symbols for the ion given are c. Co: cobalt(II) ion; Co: cobaltous ion, as they accurately reflect the correct charge of the cobalt ion (+2) and follow both the Stock system and the common naming system.
Step-by-step explanation:
The answer to the student's question is c. Co: cobalt(II) ion; Co: cobaltous ion. In naming ions, the Stock system uses Roman numerals to indicate the positive charge (oxidation state) of the ion. For example, Fe²+ would be called the iron(II) ion and Fe³+ the iron(III) ion. Likewise, in the common naming system, suffixes '-ous' and '-ic' are used to distinguish ions with lower and higher charges, respectively. The cobalt(II) ion could also be called cobaltous to reflect that it has a +2 charge, while cobalt with a +3 charge would be called cobaltic, although the Stock system is more commonly used today.
Ferrous ion and ferric ion refer to iron ions with +2 and +3 charges, respectively. Similarly, stannic ion and stannous ion refer to tin ions with +4 and +2 charges, respectively. Lead(II) ion and lead(IV) ion denote lead ions with +2 and +4 charges. Therefore, the pairs of names and symbols given as options a, b, and d in the question are not correctly matched as per the common naming system or the Stock system.