Do People Use Astronomical Gamma Ray Detectors on Earth's Surface

Multiple Choice

Do people use astronomical gamma ray detectors on Earth's surface?

A) No. The atmosphere blocks all gamma rays from space. Thus, people cannot use gamma ray detectors on Earth's surface.
B) Yes. Gamma rays have a narrow "window" through Earth's atmosphere. So, people can detect enough of them to form images.
C) Yes, but these detectors are actually pointed downward to detect rays coming through Earth. Only cosmic gamma rays have enough energy to penetrate Earth, which acts as a filter for gamma rays generated by terrestrial sources.
D) Yes, but these detectors actually detect Cherenkov radiation produced by particles struck by gamma rays high in the atmosphere. Thus, the gamma ray detection is very indirect.