From Laboratory Measurements,we Know That a Particular Spectral Line Formed

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