One Method That Has Been Used Successfully in Recent Times

Multiple Choice

One method that has been used successfully in recent times to investigate the deep interior of the Sun has been to observe

A) regular 5-minute oscillations and fluctuations of the surface.
B) the spectrum and behavior of a sunspot, whose roots are deep inside the Sun.
C) the progress of a solar-impacting comet.
D) physical conditions in the deep interior, using a spacecraft that penetrated into the Sun.