In the figure, what is the magnetic field at the point $O$

128-110

  • A

    $\frac{{{\mu _0}I}}{{4\pi r}}$

  • B

    $\frac{{{\mu _0}I}}{{4\pi r}} + \frac{{{\mu _0}I}}{{2\pi r}}$

  • C

    $\frac{{{\mu _0}I}}{{4r}} + \frac{{{\mu _0}I}}{{4\pi r}}$

  • D

    $\frac{{{\mu _0}I}}{{4r}} - \frac{{{\mu _0}I}}{{4\pi r}}$

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