Rewrite each sentence in the tense indicated. Mona Lisa smiles mysteriously.

Mona Lisa smiled mysteriously

When it comes to regular verbs, the way to create past tense is to add - ed (if the verb ends with a consonant), or - d (if the verb ends with a vowel).

So, the verb smile ends in e, which means that you only need to add - d to create past tense. The correct answer is:

Mona Lisa smiled mysteriously.