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