Answer
See below
Work Step by Step
Take $f,g \in C^0[a,b]$
$T:C^0[a,b] \rightarrow C^0[a,b]$ defined by
$T(f(x))=x$
We obtain:
$$T(f+g)=T((f+g)(x))=x\\
T(f)+T(g)=x+x=2x\\
\rightarrow T(f+g)\ne T(f)+T(g)$$
Thus it is not a linear transformation.