The correct answer is option(1). The formulas for converting between degree Celsius and degree Fahrenheit are:
$\begin{aligned}{ }^{\circ} \mathrm{F} & =\left({ }^{\circ} \mathrm{C} \times \frac{9}{5}\right)+32 \\ { }^{\circ} \mathrm{C} & =\left({ }^{\circ} \mathrm{F}-32\right) \times \frac{5}{9}\end{aligned}$
To find the temperature when both are equal, we use an old algebra trick and just set ${ }^{\circ} \mathrm{F}={ }^{\circ} \mathrm{C}$ and solve one of the equations.
$\begin{aligned} & { }^{\circ} \mathrm{C}=\left({ }^{\circ} \mathrm{C} * \times \frac{9}{5}\right)+32 \\ & { }^{\circ} \mathrm{C}-\left({ }^{\circ} \mathrm{C} \times \frac{9}{5}\right)=32 \\ & -\frac{4}{5} \times{ }^{\circ} \mathrm{C}=32 \\ & { }^{\circ} \mathrm{C}=-32 \times \frac{5}{4} \\ & { }^{\circ} \mathrm{C}=-40 \\ & { }^{\circ} \mathrm{F}=\left({ }^{\circ} \mathrm{F} \times \frac{9}{5}\right)+32 \\ & { }^{\circ} \mathrm{F}-\left({ }^{\circ} \mathrm{F} \times \frac{9}{5}\right)=32 \\ & -\frac{4}{5} \times{ }^{\circ} \mathrm{F}=32 \\ & { }^{\circ} \mathrm{F}=-32 \times 54 \\ & { }^{\circ} \mathrm{F}=-40\end{aligned}$
So the temperature when both the Celsius and Fahrenheit scales are the same is - 40 degrees.