At an International Work Conference, You Offend an Executive You

At an international work conference, you offend an executive you just met by addressing her by her first name. Which is the best intercultural explanation for this interaction?

A) Your country is individualistic; hers is collectivistic.
B) Your country is low uncertainty avoidance; hers is high uncertainty avoidance.
C) Your country is low power distance; hers is high power distance.
D) Your country is low context; hers is high context.