In western europe, the chief political repercussion of frequent viking raids was
- the strengthening of centralized royal authority.
- an increase in the power of the church.
- an increase in the power of local aristocrats to whom threatened populations turned for effective protection.
- a decline in the power of local aristocrats whose inability to stop the raids drove ordinary people into royal cities.

- an increase in the power of local aristocrats to whom threatened populations turned for effective protection.

Explanation:

The Viking leader, Hálfdan,  led the Viking army to a conquest of Mercia in 874 AD, organised a parcelling out of land among the Vikings in Northumbria in 876 AD, and in 878 AD moved south and forced most of the population of Wessex to submit. The Vikings had conquered almost the whole of England.

he sent troops to protect the students as they entered the school.