Which of the following best describes the function of the highlighted sentence? A. It undermines the assumption that human activity has had a significant impact on Earth's climate B. It supports the assumption that Earth's temperatures have risen appreciably over the past 100 years C. It questions the assumption that greenhouse gases have had a warming effect on Earth's climate D. It challenges the assumption that human activity began to affect Earth's climate after the advent of industrialization E. It supports the assumption that greenhouse gases are a direct by-product of industrial activities