Answer:
The answer is the first option "caminas".
Step-by-step explanation:
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".