Although Earth Is Estimated to Be 4-5 Billion Years Old,and

Although Earth is estimated to be 4-5 billion years old,and although life first appeared a little less than 4 billion years ago,land plants did not appear until about _______ years ago.

A) 3-4 billion
B) 400-500 million
C) 40-50 million
D) 3-4 million
E) 400,000-500,000