${ }^{n} C_{r}+{ }^{n} C_{r-1}=?$

${ }^{2 \mathrm{n}} \mathrm{C}_{\mathrm{T}}$

${ }^{n} C_{2 r}$

${ }^{2 n} C_{r-1}$

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

${ }^{2 n} C_{2 r-1}$