Correct Answer: The cat chased the mice.

Solution : The first option is the correct answer.

In the original sentence, the structure is in the passive voice, where the mice are the recipients of the action and the cat is the doer of the action. To convert it to active voice, we need to identify the doer of the action (the cat) and rearrange the sentence accordingly.

The active voice sentence in the case of the simple past tense follows the structure: subject + past form of the verb + object.

This structure places the cat as the subject, performing the action of chasing the mice, resulting in an active voice construction.

Therefore, the correct sentence is: The cat chased the mice.