Answer: Los padres les dieron su tarjeta de credito a sus hijos.
explanation: The whole sentence is: "Los padres les (dar) su tarjeta de crédito a sus hijos"
And we need to complete it with the correct preterite.
The options here are:
Preterito perfecto: refers to an action that has already been finished, the preterito perfecto in this case is "dieron"
Preterito imperfecto: refers to an action that has not ben finished the preterito imperfecto, in this case, is "daban"
And there are other preterites but are rarely used.
The Spanish sentence says something like "The parents (give) their credit card to their children"
Now, this is an action that needs to be already finished, because the act of giving someone the credit card is finished when the card changes hands, and the correct word in English would be: gave
This means that in Spanish we need to use the preterite perfecto, and the word that completes the sentence is "dieron"