If $3^{2 \sin 2 \alpha-1},14$ and $3^{4-2 \sin 2 \alpha}$ are the first three terms of an $A.P.$ for some $\alpha$, then the sixth term of this $A.P.$ is 

  • [JEE MAIN 2020]
  • A

    $66$

  • B

    $65$

  • C

    $81$

  • D

    $78$

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