The family used to visit the grandparents for their anniversary. la familia visitaba a los abuelos para su aniversario. la familia visitó a los abuelos para su aniversario. la familia visitando a los abuelos para su aniversario. la familia fue a visitar a los abuelos para su aniversario.

Right La familia visitaba a los abuelos para su aniversario.

This is a good example of the usage of the Preterite in Spanish, this verbal tense is used when you wanto to:

1. talk about past habitual actions, (adding used to in its different forms), to describe what used to happen or what was happening

2. describe what someone was doing when it was interrupted by someone (or something) else.  

In this sentence:

The family used to visit the grandparents for their anniversary

We are talking about the first case, because this was an action that was taking place at that time in the past, and we can see the used to, as well.

Now, the preterite of the spanish verb visitar (to visit) with the 3rd person in plural ellos (they), which are The family, is visitaban. Therefore the complete sentence is:

La familia visitaba a los abuelos para su aniversario.

Select the word from the list that best fits the definitionstates the the universe is expanding

Doulingo is good. you can also watch movies that are in french, i am using this tactic  for japanese  and it a lot. listing to music with  french  lyrics would work well too because  you could absorb  the words while having fun.hope this ! : )