Question

Please select the preterite form of the verb that best fits the sentence. They were climbing a tree when they fell.

Answer 1

Ellos estaban subiendo un arbol cuando se cayeron.

Answer 2

Ellos estaban subiendo al árbol cuando se cayeron.

Step-by-step explanation:

In this case, we use past continuous to express a background action (were climbing) of the main action that is in past simple (they fell)