In Choose odd pair of words type of questions, certain pairs of words are given out of which the words in all the pairs except one, bear a certain common relationship. The candidate is required to decipher this relationship and chose the pair in which the words are differently related, as the answer.
(Solder : Tin) , (Haematite : Iron) , (Bauxite : Aluminium) , (Malachite : Copper)
In all other pairs,first is the name of a metal of which the second is an ore.
On the other hand, Solder is an alloy.