The eigen vectors of the matrix \[\left[ {\begin{array}{*{20}{c}} 1&2 \\ 0&2 \end{array}} \right]\]  are written in the form \[\left[ {\begin{array}{*{20}{c}} 1 \\ {\text{a}} \end{array}} \right]\] and \[\left[ {\begin{array}{*{20}{c}} 1 \\ {\text{b}} \end{array}} \right].\]  What is a + b = ?

A. 0

B. \[\frac{1}{2}\]

C. 1

D. 2

Answer: Option B