Why is filial piety the “source of all virtues” in Confucianism?

Question

A.
because Confucius believed it is the model for the other four relationships

B.
because Confucius believed soldiers should be honored for their duty above the family

C.
because Confucius believed equality in relationships was the basis for the other four relationships

D.
because Confucius believed people should behave properly in order to avoid punishments
I think it might be A but im not sure.

Answer 1

A is correct.

https://en.wikipedia.org/wiki/Filial_piety