${ }^{n} C_{r}+{ }^{n} C_{r-1}$ এর মান কোনটি ?

$n^{n+3} C_{r-1}$

${ }^{n-3} C_{r+1}$

${ }^{n+3} \mathrm{C}_{1}$

${ }^{n+1} C_{r}$

${ }^{n-1} C_{r-1}$