61.The event horizonA.is believed to be a singularity.B.is a crystalline layer.C.has a radius equal to the Schwarzschild radius.D.marks the inner boundary of a planetary nebula.E.is located at the point where synchrotron radiation is created around a pulsar. 62.An isolated black hole in empty intergalactic space would be difficult to detect becauseA.there.
- 61.The event horizonA.is believed to be a singularity.B.is a crystalline
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