how to fill in a form for personal info

[optimistic pessimist]

Dear all,
When you fill in a form for personal info, which is better, A or B?
:
religion : A. Christian B. Christianity
nationality : A. Japan B. Japanese

Thank you

OP

[SoothingDave]

I would use the "A" form for both. It's less to write. There is little risk of confusion.

[5jj]

religion : A. Christian
nationality : B. Japanese.This is presumably for a country in which it is acceptable to enquire about your religion.

It might be relevant to add your branch - Christian (Roman Catholic), for example - if this is relevant.

[SoothingDave]

I always just write "USA" for nationality, when asked. "American" can seem domineering when everyone from the hemisphere has a valid claim to be such.

If I asked someone's religion, I would expect to hear "Catholic" and not "Catholicism."