Add the correct punctuation mark from the given options.

That is a watermelon   _______

The correct answer is: Full stop (.)

A full stop (.) is chiefly used to end a sentence. It is mostly used at the end of declarative sentences. A full stop marks a longer pause than a comma and a semicolon. Furthermore, it marks the end of a thought and the beginning of another. 'This is a watermelon.' Here full stop marks the end of a thought.