Choose the word opposite in meaning to the italicized word.
The police tried to identify the rightful owner of the ornaments left in the train.

a) Indefinite
b) Mistaken
c) Unlawful
d) Claimant

Hint: Meaning of Rightful – Rightful means to have legitimate position or status.
Opposite of Rightful should mean something that is not legitimate.

Complete answer:

 Option a ‘Indefinite’ is the word given to something which is stressed over an unknown length or period of time. The word has no relation with the given word and hence is incorrect.
Option b ‘Mistaken’ means to be incorrect or wrong in someone’s opinion or judgment. This word has no connection with the meaning of the given word and hence is incorrect.
Option c ‘Unlawful’ means something that is not recognized by the law. The meaning of unlawful has similarity with the meaning of the antonym of rightful and it also satisfies the motive of the statement given. So, this option is the correct option.
Option d ‘Claimant’ is a person who asserts that a specific thing belongs to him. The meaning has no connection with either the synonym or antonym of the given word. So, this option is not the correct option.

Note: The meaning of the word should be kept in mind and understood to find the suitable opposite.