TOEFL Listening: ETS-TOEFL听力机经 - M43Z5OP31VLNDPN1P$

What is the lecture mainly about? A. Why the chemical composition of some exoplanets prevents them from being detected. B. A recent discovery of an exoplanet that has prompted are invention of the vortex coronagraph. C. Enhanced techniques for observing planets outside our solar system. D. Some common misunderstandings about powerful telescopes.