Gamma-Ray "Bubbles" Have Been Found Above and Below the Plane

Gamma-ray "bubbles" have been found above and below the plane of our galaxy. (See Figure 22-30 of Universe, 11th ed.) These are:
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A) relatively small regions within the central bulge that are probably remnants of jet activity from Sagittarius A*.
B) regions from which no gamma-ray emission has been observed.
C) huge regions in which gamma rays are produced when high-speed electrons interact with photons of energies below the gamma-ray range.
D) the first gamma-ray bursters to be observed within our galaxy.