Because when you are saying yo, you could be talking in present, past, or future tense. The word yo, in the Spanish language, does not specify which tense it is in until we look at the verb in the sentence.
1. my favorite food is pizza
mi comida favorita es la pizza.
2. i do not like the chicken
No me gusta el pollo
puedo usar mis cheques de viajero para efectivo?
