A) 45
B) 50
C) 90
D) 100
Correct Answer: A
$ \therefore $ Total number of handshakes $ ={}^{10}C _2 $ $ \because $ $ {}^{n}C _{r}=\frac{n!}{r!(n-r)!}=\frac{10!}{2!(10-2)!} $ $ =\frac{10\times 9\times 8!}{2\times 1\times 8!}=\frac{10\times 9}{2}=45 $