The correct answer is D. More African elephants today naturally lack tusks compared to the elephant populations 100 years ago, because big game hunters sought elephants for ivory.
Explanation:
In biology, selection occurs as certain organisms with adaptative characteristics prevail over time as they are more likely to reproduce and survive, while organisms with other characteristics disappear. This process can occur by artificial means as human beings intervene in selection.
According to this, the one that is an example of artificial selection is "More African elephants today naturally lack tusks compared to the elephant populations 100 years ago, because big game hunters sought elephants for ivory", because in this case, elephants without tusks are more likely to survive and reproduce and due to this, they are more common today which explains selection. However, this process occurred mainly because of poachers which means there is intervention from human beings and therefore the selection is artificial.