Clothing. The Samurai wore flexible armor made of scales. The knights did this. The Samurai did not. The Samurai protected themselves with an extreme skill based on hand to hand combat techniques.
They both had a code that governed their behavior. The Samurai would never think of breaking that code, although I'm sure it was done. They were loyal to the point of rigidity. Though it was different, the knights were the same way.
Both received land for loyalty.
C and A are similar and both classes of people did both in different forms.
Answer B
