The correct answer is A. Voy a una jineteada.
Since you need to translate the word 'I' into Spanish, which is 'Yo,' you also need to use the appropriate verb form for that particular pronoun, which is voy, in this case. Vas is for you/tu, va is for he/she/it (el, ella, usted), and van is for they (ellos, ellas, ustedes).
