Under which one of the following condition does the system of equations \(\left[ {\begin{array}{*{20}{c}} 1&2&4\\ 2&1&2\\ 1&2&{a - 4} \end{array}} \right]\left[ {\begin{array}{*{20}{c}} x\\ y\\ z \end{array}} \right] = \left[ {\begin{array}{*{20}{c}} 6\\ 4\\ a \end{array}} \right]\) have a unique solution?

• A. a = 8
• B. a ≠ 8
• C. For all a ϵ R
• D. For all a ϵ Z