Si vas a comprar una cola, es fácil usar a. la agencia de viajes c. el efectivo b. los cheques de viajero d. el pasajero

El efectivo translates into the cash and this is the easier form of payment because you use bills and coins and is faster to pay with this. The other options are not logical to be chosen because la agencia de viajes that means the travel agency, los cheques de viajero that means traveler's checks and el pasajero that means the passenger.