Answer:
The correct option is "told"
Step-by-step explanation:
As it can be seen, most of the abstract provided, belonging to the introduction to Kenny’s personal narrative, “Best Friends.” is written in past tense; either past perfect, past progressive or simple past. Therefore, from the options of the verb (to) tell listed, the one that correctly would fill the blank is "told".
In this sense, the sentence would result as follow: So when Karim’s parents told us that they were moving across the country, we didn’t believe it, and we didn’t know how our friendship would survive.