What Caused the Rise of Youths, Unmarried Knightly Vassals Who

Multiple Choice

What caused the rise of youths, unmarried knightly vassals who lived with their lords for indefinite periods of time?

A) The increasing power of local lords made it desirable to maintain a number of household knights for defensive purposes.
B) The violence among territorial rulers created a class of unmarried knights committed to war and prepared to enter battle with little advance preparation.
C) The introduction of primogeniture (bequeathing an entire estate to the eldest son) left younger sons without property, unable to marry, and dependent upon their lords.
D) The newly powerful local rulers preferred to marry their daughters to distant nobles, and knightly vassals preferred to remain single rather than marry a social inferior.