The major obligation of the lord to the vassal was

A) Economic support and protection either militarily or through grants of land.

B) Scutage.

C) The tithe.

D) Free use of the manorial mill.

E) To arrange the marriages of the vassal's children.

The right ansewer is A

Explanation:

It is necessary to keep in mind that the feudal lord is the maximum authority within a given area, he owns the land, money, and power over people.

In case of any attack or looting of enemies the feudal lord is in charge of organizing the army or battle group and protecting their vassals, their lands and their property.

Also this, being the owner of large tracts of land, handed them over to peasants to work for money or grain.

It is also possible that the feudal lord makes loans to peasants or artisans to buy goods necessary for production (such as horses, plows or tools for blacksmithing or cloth).

Option B and C correspond to an obligation of the vassal to the feudal lord.

Option D, the use of the mill was not always free.

and finally in option E the parents are the ones who had the power to choose marriage for their children, in many regions this marriage had to be approved by the feudal lord.