X-Ray Telescopes in Space Are Primarily Used for Examining Which

Multiple Choice

X-ray telescopes in space are primarily used for examining which kind of environment in the universe?

A) Extremely cool regions of space,because only X-rays can penetrate them
B) Extremely hot regions around stars and galactic centers
C) The deep interiors of normal stars from which only the penetrating X-rays can escape
D) Comets and planets