- ✓$0$
- B$1$
- C$2$
- D$3$
$ = \left( {\begin{array}{*{20}{c}}
{16} \\
9
\end{array}} \right) - \left( {\begin{array}{*{20}{c}}
{16} \\
7
\end{array}} \right)\,\,\,\left[ {\left( {\begin{array}{*{20}{c}}
n \\
r
\end{array}} \right) + \left( {\begin{array}{*{20}{c}}
n \\
{r - 1}
\end{array}} \right) = \left( {\begin{array}{*{20}{c}}
{n + 1} \\
r
\end{array}} \right)} \right]$
$ = \left( {\begin{array}{*{20}{c}}
{16} \\
9
\end{array}} \right) - \left( {\begin{array}{*{20}{c}}
{16} \\
{16 - 7}
\end{array}} \right)\,\,\,\left[ {\because \left( {\begin{array}{*{20}{c}}
n \\
r
\end{array}} \right) = \left( {\begin{array}{*{20}{c}}
n \\
{r - 1}
\end{array}} \right)} \right]\,\,$
$ = \left( {\begin{array}{*{20}{c}}
{16} \\
9
\end{array}} \right) - \left( {\begin{array}{*{20}{c}}
{16} \\
9
\end{array}} \right) = 0$
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