The correct answer is:
a. una tarjeta telefónica
Explanation:
1. In Spanish, the question is asking what is needed to make a phone call when you don't have money.
2. The correct answer is "una tarjeta telefónica" which translates to a phone card. This card is used to pay for phone calls when you don't have money or credit on your phone.
3. The other options (c. una tecla, b. una ranura, d. un botón) do not correspond to the item needed to make a phone call without money.
