Solution:

The wife booked a two way ticket for herself and booked a one way ticket for her husband.

Solution:

They can neither be true nor be false. They contradict each other and these statements are known as paradox.

Solution:

The third son bought a candle and a matchstick. He lighted the candle from the matchstick and the light filled the entire room.

Solution:

There are only four cats. The room is too small and each cat is sitting at the tail of other.

Solution:

SH

Explanation :
If you look closely, you will see that the first letter of every set is moving 6 alphabets forward while the second one is moving six alphabets backwards.

Solution:

As we can catch 'Cold', 'Hot' is definitely faster.

Solution:

It is perfectly possible. The sailors were looking across the deck at each other and not at the sea.

Solution:

Quadratic

Explanation:

quad(4 wheeler)
+ rat
+ i (eye)
+ C

Solution:

Periodic Table

Solution:

silver spoon