TOEFL Listening: ETS-TOEFL听力机经 - 5B19O9Z53Q3L13AYP$

What is a typical characteristic of dark nebulae? A. They are obscured from view by nearby stars. B. They are located in parts of the sky that do not contain bright stars. C. The dust and gas they contain are too dense to let light through. D. They are too hot to emit radiation in the visible range.