It has been observed that herd animals exhibit a variety of responses to a threat. Some individuals freeze, others run, while still others bunch tightly
with their group. Which of the following statements most directly supports
the claim that this observed variation in behavior is genetically determined?
A. Deer with strong reactions to being approached by humans were
found to have higher heart rates.
B. Antelopes housed in a zoo enclosure can be habituated to having
their blood drawn for medical tests.
C. Temperament differences in sheep have been found to be stable
over time.
D. Young cattle sired by certain bulls are more excitable than cattle
sired by other bulls.