TOEFL Listening: ETS-TOEFL听力机经 - 1Q31K1K3HA496X1SP$

Why does the professor mention isotopes of hydrogen? A. To correct a student's comment about how fusion takes place in stars B. To help answer a student's question about temperature requirements for fusion reactors C. To explain what happens to hydrogen atoms during fusion reactions D. To justify the need for superconducting magnets in nuclear fusion reactors