Given,
f(x)=max1+x+[x],2+x,x+2[x],0≤x≤2
\Rightarrow f(x)={\begin{matrix}\mathrm{max}{x+1,x+2,x} & 0\leq x<1 \\ \mathrm{max}{x+2,x+2,x+2} & 1\leq x<2 \\ \mathrm{max}{5,4,6} & x=2\end{matrix}
\Rightarrow f(x)={\begin{matrix}x+2, & 0\leq x<1 \\ x+2, & 1\leq x<2 \\ 6, & x=2\end{matrix}
\Rightarrow f(x)={\begin{matrix}x+2 & 0\leq x<2 \\ 6 & x=2\end{matrix}
So, f is not continuous at x=2 as f({2}^{-})=4&f(2)=6
And f is differentiable in (0,2) as x+2 is a linear function,
∴m=1,n=0
⇒(m+n)2+2=1+2=3
Hence this is the required option.