A larger vertical distance above the line does not always mean a larger percent greater value. Divide each positive residual by the value predicted by the line.

For each answer choice, substitute its sunlight value into the line's equation before calculating the relative difference.

Algebra is quick here. For a Desmos check, enter $f(x)=6x+9$, using the two labeled points on the line of best fit.

In a table, enter the four candidate sunlight values in one column and their observed energy values in a second column.

Create a third column with $r_1=(y_1-f(x_1))/f(x_1)$. Desmos displays the four relative differences; select the point corresponding to the largest positive value.

The line passes through $(2,21)$ and $(14,93)$. Its slope is $\frac{93-21}{14-2}=6$, so its equation is $y=6x+9$.

For each choice, find $\frac{\text{observed}-\text{predicted}}{\text{predicted}}$. The ratios are $\frac{5}{45}$ for $(6,50)$, $\frac{13}{57}$ for $(8,70)$, $\frac{11}{69}$ for $(10,80)$, and $\frac{12}{33}$ for $(4,45)$.

The ratio $\frac{12}{33}$ is the greatest of the four. Therefore, the point with the greatest percent greater observed energy production is $(4,45)$.