Historically, African elephants have had large ivory tusks. For many years, poachers (illegal hunters) have been killing elephants that have large tusks so they could sell the ivory, which is valuable. Now, many African elephants have small tusks or do not develop tusks. Which of the following is true?
a. The trait of tusk size in elephants has changed over time.
b. Poaching has had no effect on the size of elephant tusks.
c. Elephants without tusks are more likely to be hunted than elephants with large tusks.
d. Elephants without tusks cannot reproduce.