When we conjugate the verb caminar (to walk) in the indicativo presente mood in Spanish, this is what we have:
yo camino
tú caminas
él/ella camina
nosotros caminamos
vosotros camináis
ellos/ellas caminan
Therefore, if the question wants us to conjugate it as "you walk" in English, we will have "tú caminas" in Spanish, since tú = you. Since the conjugation is enough to show to which person (first, second, or third; singular or plural) the verb refers, we may very well leave out the pronoun "tú", and say only "caminas".
The correct answer among all the other choices is a. formality. This is not something to consider when revising for clarity. Thank you for posting your question. I hope this answer helped you. Let me know if you need more help.
