(i)-(b), (ii)-(a), (iii)-(d), (iv)-(e), (v)-(c)

(i)-(b) Lanthanoid oxides are used in television screens.

(ii)-(a) Lanthanoids are mixed with iron to form an alloy

(iii)-(d) Misch metal is an alloy of lanthanoids(95%) and iron(5%) and traces of S,Si, Al,Cetc

(iv)-(e) Magnesium alloy is used to make bullets

(v)-(c) Petroleum cracking involves breaking down complex organic molecules into simpler hydrocarbons. Mixed oxides of lanthanoids are used as catalyst for petroleum cracking.