Read the list of sentences from the article.

1. carbon dioxide concentrations have skyrocketed far higher than any levels in more than 800,000 years, according to data from the scripps institution of oceanography at the university of california, san diego.

2. "not just in recorded history, not just since the invention of agriculture 10,000 years ago. since before modern humans existed millions of years ago."

3. carbon dioxide levels millions of years ago were higher than 2019 levels, but earth's temperatures were also far higher.

4. in the 800,000 years before the industrial revolution, co2 levels didn't surpass 300 parts per million.

which two sentences taken together provide the best evidence to support the idea that the co2 levels we are experiencing now are abnormal?

a
1 and 3
b
1 and 4
c
2 and 3
d
2 and 4