Answer
$$\text{G}$$
Work Step by Step
Recall:
The corresponding sides of two similar triangles are proportional.
The two triangles are similar therefore their corresponding sides are propertional.
Thus,
\begin{align*}
\frac{\text{BC}}{\text{EF}} &= \frac{\text{AC }}{\text{DF}}\\\\
\frac{6}{9} &=\frac{k}{6}
\end{align*}
Cross-multiply to obtain:
\begin{align*}
9(k)&=6(6)\\
9k&=36\\
\frac{9k}{9}&=\frac{36}{9}\\
k&=4
\end{align*}
Hence, $k=4\text{ ft}$.
