Answer:
a-1, b-2, c-1, d-1
Explanation:
Let us look at the first compound- OsN2
Since osmium is in +6 oxidation state and nitrogen is in -3 oxidation state. The valency of the species are 6 for osmium and 3 for nitrogen. They can now exchange valencies and we have Os3N6. Reducing to the lowest term we now have OsN2 as the formula of osmium nitride.
Similarly, rhodium is triply bonded to carbon to form the compound RhC in which the rhodium and carbon share six electrons. There is one sigma bond and two pi bonds between the atoms of rhodium and carbon.
