TOEFL Listening: ETS-TOEFL听力机经 - 5PCW342P_1MQ9P1XP$

What does the professor imply when he says this: A. It is very difficult to detect an exoplanet, regardless of the method used. B. Astronomers are not satisfied with the amount of information indirect methods of detection provide. C. Some direct methods of detection are less useful than indirect methods for detecting exoplanets. D. The exact location of an exoplanet can be confirmed by detecting a wobble in the parent star.