Answer:
The right answer is, C. Madrastra.
* Yo iba a la boda de mi papá con su segunda esposa Lucía. Ella es mi madrastra.
Explanation:
because according to the previous text, who narrates is telling that his father is going to marry a woman who is not his mother, this means that he is his stepmother, therefore the option that describes this situation is C.
Ellos Means they not you all. You all is Nostros.
So its Incorrect. :)
I would say the first would be usted and the second one would be nosotros
Hope this helps :)