Find the word in given series of words that has the same relationship to the third word as that between first two.

Touch : Feel :: Greet : ?

Acknowledge

Hint,

When we touch someone it is felt. The first word is the action and the second word is the reaction/consequence.

Similarly, when we greet someone it is acknowledged.

Smile → The expression of happiness

Success → It is the state when a person achieve what he wants.

Manners → The way someone does something.

Acknowledge → To show that you have received or noticed something that the other person did for you.

Hence, "acknowledge" is the correct option.