Who's duty was it to give land, protect his knights from attack, and resolve disputes between knights?

It was the Lord’s duty.

Explanation:

A Lord is elected by the Congress or gets the title from birth. A knight were soldiers who had special training in combats and were involved in various warfares. The Knights are answerable to the Lords.

The Lord’s duty to the Knights was to give them land, protect them from attack and help in resolving disputes between knights.

b) race riots in several cities