Reasoning

All except Wife are elderly people.

Mercury is the only liquid metal in the group.

All except Aluminium are magnetic materials.

All except Again denote certain period of time.

In all other pairs, first is the means of transport on the medium denoted by the second.

All except Parrot are birds of prey.

All except Whale belong to the family of fishes, while whale is a mammal.

All except Kangaroo have thick hair or fur on their skin.