Under the feudal system, a higher noble granted land to a lower noble in exchange for
a)a portion of the lower noble's crop yield.
b)an oath of loyalty.
c)the use of the lower noble's serfs.
d)a payment in the form of money or livestock

i think the answer will be

B:

an oath of loyalty.

during the 20th century, the role of the vice president has evolved into more of an executive branch position. now, the vice president is usually seen as an integral part of a president's administration and presides over the senate only on ceremonial occasions or when a tie-breaking vote may be needed.