If $n$ and $r$ are two positive integers such that $n \ge r,$ then $^n{C_{r - 1}}$$ + {\,^n}{C_r} = $
If $n$ and $r$ are two positive integers such that $n \ge r,$ then $^n{C_{r - 1}}$$ + {\,^n}{C_r} = $
- A
$^n{C_{n - r}}$
- B
$^n{C_r}$
- C
$^{n - 1}{C_r}$
- D
$^{n + 1}{C_r}$
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