When Excited Electrons Decay to Ground State,hydrogen Emits Along Distinctive

Multiple Choice

When excited electrons decay to ground state,hydrogen emits along distinctive line near the visible red.An astronomer observes what appear to be hydrogen emission lines from a distant star but they are in the infrared spectral band.She concludes ________.

A) her instrument needs to be recalibrated
B) the star must be moving very fast away from Earth
C) the star must be moving very fast toward Earth
D) the star's hydrogen emission must be being absorbed by water in the atmosphere,which then re-emits in the infrared