Find a basis for the space of $2 \times 2$ diagonal matrices.

Basis = $\Bigg\lbrace$ $\left[\Rule{0pt}{2.4em}{0pt}\right.$ $\left]\Rule{0pt}{2.4em}{0pt}\right.$, $\left[\Rule{0pt}{2.4em}{0pt}\right.$ $\left]\Rule{0pt}{2.4em}{0pt}\right.$ $\Bigg\rbrace$