Use the iupac nomenclature rules to give the name for this compound - cas.

a)
calcium sulfide

b)
calcium (ii) sulfide

c)
dicalcium trisulfide

d)
calcium (iii) sulfide

Option A, calcium sulfide

Explanation:

As per the IUPAC nomenclature rule for inorganic compound –  

a)If cation name must come before the anion name , then no prefixes are required with the cation to show its valency

b)In case anion name comes first then prefixed such as double, triple, etc. shall be added in the anion name. The number here represents the  variety of cation present and not the total number of cation

Here, calcium is cation and its name is placed before the anion and hence the name calcium sulfide is ok

the scientific method.