Which of the following statements are TRUE? (Select all that apply)

(i) The matrix $\begin{pmatrix} 2 & 6 \\ 1 & 3 \end{pmatrix}$ is singular.

(ii) The matrix $\begin{pmatrix} 1 & 0 & 0 \\ 0 & 2 & 0 \\ 0 & 0 & 3 \end{pmatrix}$ is singular.

(iii) The matrix $\begin{pmatrix} 1 & 2 & 3 \\ 2 & 4 & 6 \\ 3 & 6 & 9 \end{pmatrix}$ is singular.