$^{20}C_1 + 3 ^{20}C_2 + 3 ^{20}C_3 + ^{20}C_4$ is equal to-

  • A

    $^{20}C_4$

  • B

    $2. ^{21}C_4$

  • C

    $2. ^{22}C_4$

  • D

    $^{23}C_4$

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