Change the narration: My sister said, "I walk to school while others go by bus".

My sister exclaimed that he walks to school while others go by bus.

My sister said she walks to school while others go by bus.

My sister told that she walks to school while others go by bus.

None of these

My sister said she walks to school while others go by bus.

The reporting verb is "said" and the sentence expresses a habitual action (present simple).

Present simple tense remains unchanged in indirect speech if the statement expresses a general truth or habit.