The sum of \({ }^{20} C_{8}+{ }^{20} C_{9}+{ }^{21} C_{10}+{ }^{22} C_{11}-{ }^{23} C_{11}\) is
Using this formula \({ }^{n} C_{r}+{ }^{n} C_{r-1}={ }^{n+1} C_{r}\) \[\] \({ }^{20} C_{8}+{ }^{20} C_{9}+{ }^{21} C_{10}+{ }^{22} C_{11}-{ }^{23} C_{11}\) \[\] \({ }^{21} C_{9}+{ }^{21} C_{10}+{ }^{22} C_{11}-{ }^{23} C_{23}\) \[\] \({ }^{22} C_{10}+{ }^{22} C_{11}-{ }^{23} C_{11}\) \[\] \({ }^{23} C_{11}-{ }^{23} C_{11}=0\) \[\] Choice (C)
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