Which of the following does not belong to the group formed by the others?
(A) Iron
(B) Tin
(C) Glass
(D) Steel

Hint: We are asked to find the odd one from the given four options. We can easily spot the odd one out based on a number of properties. We can see what the majority of them have in common. Then we can spot the odd one leading us to our answer

Complete Step By Step Answer:
Let us start to answer this question by categorizing the items into metals or not. This is done because we have our first option as, iron. Iron and tin are metals. Steel however is a metal alloy which is made from iron. This lets us believe that the odd one is not picked out based on if it is a metal or not.
Next, we move onto conductivity. Iron, tin and steel are able to conduct while glass is not. This makes glass the odd one.
Glass does not conduct electricity because it does not have free mobile ions. In conductors, the mobile ions act as a medium for the electricity to pass through and glass does not have the free mobile ions.
In conclusion, the right answer is option (C) Glass.

Note:
Conductors are materials that allow electricity to pass through. Metals are very good examples of conductors. Insulators are those materials which do not allow electricity to pass through. Rubber, glass and wood are some of the examples of insulators.
Materials are classified into one more category called semiconductors which are able to conduct only at a certain temperature. At lower temperatures they act as insulators.