Although Humans Appear to Be Responsible for the Current Extinction

Although humans appear to be responsible for the current extinction crisis, scientists are confident that human did not contribute to any previous extinction event because

A) humans did not exist during those time periods.
B) the human population 350 million years ago was too small to have caused any environmental problems.
C) humans lacked the modern technologies in use today that cause so much environmental damage.
D) aggressive predatory dinosaurs have been shown to be responsible for these extinctions.