[单选题]
The graph shows the numbexjiaso,unfjm..i55r +p gihi m -4/ (or of female African ele6 m9) xq)u twnwe/ fl4a9+mfvdphants (Loxodonta africana) born without tusks in Gorongo+6anwqfd )xm49/u f9tlv) em wsa National Park. How does natural selection explain the trend shown in the graph?
A. Elephants broke their tusks while fighting, and their offspring were born without tusks.
B. Poachers hunted elephants with tusks, resulting in increased survival of elephants without tusks.
C. Elephants born without tusks are better fighters so survived better.
D. Mutations resulting in no tusk formation started to happen more often.
