Answer:
Option D. Industry and dedication to a strong work ethic
Step-by-step explanation:
Option A is not correct as druids were their spiritual and even religious leaders, who had large importance in the society.
B also is not correct as their leaders were at the top of social hierarchy.
C is not correct as with the spreading of Christianity monasticism became really important, especially during the reign of Alfred the Great.
D is not correct as industry did not existed in the period when these tribes dominated.