TOEFL Listening: TPO-TOEFL阅读TPO - BJ2E634W1W85LI11N$

According to paragraph 1, petroleum is formed in which of the following ways? A. Bacteria and tiny plants undergo a change while they are buried in clay. B. Carbon and hydrogen combine to form shale. C. Ocean rocks are converted into organic compounds. D. Oil and gas rise to the surface of sediment and are trapped in rocks.