challenge: According to the proposed scenario, what was the outcome of the merger between the neutron star and the red giant's core?
  
  A. A supernova with no gamma-ray emission
  B. The birth of a black hole or a magnetar and the production of oppositely directed jets of particles
  C. The formation of a stable binary system with a neutron star and a black hole
  D. A massive helium star with an expanded outer atmosphere
  Answer: 