The letters Q.E.D. at the end of a proof mean:

  1. which was to be demonstrated (the proof is complete)
  2. question ends directly
  3. quite easily done
  4. the next step follows
Answer

A) which was to be demonstrated (the proof is complete)

Q.E.D. — quod erat demonstrandum. SLO M-09-B-13 · Knowledge

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