$${\textbf{Step -1: Considering option A.}}$$
$${\text{We have given,}}$$
$$x - 5 = 1$$
$${\text{Putting }}x = - 1{\text{ we get,}}$$
$$ - 1 - 5 = 6$$
$$ \Rightarrow - 6 = 1$$ $${\text{Which is not possible}}{\text{.}}$$
$${\text{Here,
L}}{\text{.H}}{\text{.S}} \ne {\text{R}}{\text{.H}}{\text{.S }}$$
$${\text{So, - 1 is not a solution of }}x - 5 = 6.$$
$${\textbf{Step -2: Considering option B.}}$$
$${\text{We have given,}}$$ $$2x
+ 5 = 7$$
$${\text{Putting }}x = - 1{\text{ we get,}}$$
$$2\left( { - 1} \right) + 5
= 7$$
$$ \Rightarrow - 2 + 5 = 7$$
$$ \Rightarrow 3 = 7$$ $${\text{Which
is not possible}}{\text{.}}$$
$${\text{Here,
L}}{\text{.H}}{\text{.S }} \ne {\text{ R}}{\text{.H}}{\text{.S }}$$
$${\text{So, - 1 is not a solution of 2}}x + 5 = 7.$$
$${\textbf{Step -3: Considering option C.}}$$
$${\text{We have given,}}$$ $$2\left(
{x - 2} \right) + 6 = 0$$
$${\text{Putting }}x = - 1{\text{ we get,}}$$
$$2\left( { - 1 - 2} \right)
+ 6 = 0$$
$$ \Rightarrow 2\left( { -
3} \right) + 6 = 0$$
$$ \Rightarrow - 6 + 6 = 0$$
$$ \Rightarrow 0 = 0$$
$${\text{Which is possible}}{\text{.}}$$
$${\text{Here,
L}}{\text{.H}}{\text{.S = R}}{\text{.H}}{\text{.S }}$$
$${\text{So, - 1 is a solution of 2}}\left( {x - 2}
\right) + 6 = 0.$$
$${\textbf{Step -4: Considering option D.}}$$
$${\text{We have given,}}$$ $$3x
+ 5 = 4$$
$${\text{Putting }}x = - 1{\text{ we get,}}$$
$$3\left( { - 1} \right) + 5
= 4$$
$$ \Rightarrow - 3 + 5 = 4$$
$$ \Rightarrow 2= 4$$
$${\text{Which is not possible}}{\text{.}}$$
$${\text{Here,
L}}{\text{.H}}{\text{.S}} \ne {\text{R}}{\text{.H}}{\text{.S }}$$
$${\text{So, - 1 is not a solution of }}3x + 5 = 4.$$
$${\textbf{ Hence, option C}}{\textbf{. 2}}\left(\mathbf {x - 2} \right)\mathbf{ + 6 = 0}{\textbf{
is correct answer.}}$$