Scientists estimate that for more than _______ years after cells originated, all organisms consisted of one cell.
a. 2,500
b. 250,000
c. 2.5 million
d. 2.5 billion
e. 2.5 trillion
Answer: D
Scientists estimate that for more than _______ years after cells originated, all organisms consisted of one cell.
a. 2,500
b. 250,000
c. 2.5 million
d. 2.5 billion
e. 2.5 trillion