Read the following context and choose the best option to answer the question.
Context: They were really nice and the grandma was so sweet . The grandpa asked when Oma left Germany , and I said around ' 55 and he nodded and said , " She was right , she was right , " So that was funny . The grandmother 's name is Johanna , but I do n't know the grandfather 's name .
Question: What may be the reason why they do n't know the grandfather 's name ?
Options: 
A. None of the above choices .
B. They were n't supposed to know it .
C. They are undercover .
D. They are in the witness protection program .


A