Solution:
In all other pairs, lack of first causes the second.

Solution:
All except Sword strike the target at a distance.

Solution:
All except Trousers are garments which cover the upper part of the body.

Solution:
All except Iron are very volatile.

Solution:
In all other groups, the first and second letters are moved 4 steps backward to obtain second and third letters respectively.

Solution:
All except Quay are parts Of a ship.

Solution:
All other groups consist of alternate letters.