Ultraviolet Radiation with a Wavelength Shorter Than About 200 Nm

Multiple Choice

Ultraviolet radiation with a wavelength shorter than about 200 nm is hard to observe primarily because

A) Earth's atmosphere easily absorbs it.
B) no space-based telescopes operate at ultraviolet wavelengths.
C) only the lowest-mass stars emit ultraviolet light.
D) very few objects emit at ultraviolet wavelengths.
E) Earth emits too much ultraviolet background light.