Which one of the following matrices is singular?

A. \[\left[ {\begin{array}{*{20}{c}} 2&5 \\ 1&3 \end{array}} \right]\]

B. \[\left[ {\begin{array}{*{20}{c}} 3&2 \\ 2&3 \end{array}} \right]\]

C. \[\left[ {\begin{array}{*{20}{c}} 2&4 \\ 3&6 \end{array}} \right]\]

D. \[\left[ {\begin{array}{*{20}{c}} 4&3 \\ 6&2 \end{array}} \right]\]

Answer: Option C