Ans: B
Since $h$, $5$ and $k$ form an arithmetic sequence, then we have
Since $h$, $5$ and $k$ form an arithmetic sequence, then we have
$\begin{array}{rcl}
h + k & = & 2 \times 5 \\
h + k & = & 10 \ldots \unicode{x2460}
\end{array}$
Since $h$, $4$ and $k$ form a geometric sequence, then we have
$\begin{array}{rcl}
hk & = & 4^2 \\
hk & = & 16 \ldots \unicode{x2460}
\end{array}$
Hence by $\unicode{x2460}$ and $\unicode{x2460}$, we have
$\begin{array}{rcl}
(h+k)^2 & = & 10^2 \\
h^2 +2hk + k^2 & = & 100 \\
h^2 + k^2 +2(16) & = & 100 \\
h^2 + k^2 & = & 68
\end{array}$
