From Laboratory Measurements, We Know That a Particular Spectral Line

Multiple Choice

From laboratory measurements, we know that a particular spectral line formed by hydrogen appears at a wavelength of 121.6 nanometers (nm) . The spectrum of a particular star shows the same hydrogen line appearing at a wavelength of 121.8 nm. What can we conclude?

A) The star is getting hotter.
B) The star is moving toward us.
C) The "star" actually is a planet.
D) The star is moving away from us.
E) The star is getting colder.