Ans: B
Let $\mu$ marks be the mean marks of the examination.
Let $\mu$ marks be the mean marks of the examination.
$\begin{array}{rcl}
\dfrac{69 – \mu}{8} & = & 0.5 \\
69 – \mu & = & 4 \\
\mu & = & 65
\end{array}$
Let $x$ marks be the examination score of John.
$\begin{array}{rcl}
\dfrac{x – 65}{8} & = & -1.5 \\
x – 65 & = & -12 \\
x & = & 53
\end{array}$
Therefore, the examination score of John is $53$ marks.
