\begin{tabular}{|l|l|}
\hline Q.10 & $\begin{array}{l}\text { An opaque pyramid (shown below), with a square base and isosceles faces, is } \\
\text { suspended in the path of a parallel beam of light, such that its shadow is cast on a } \\
\text { screen oriented perpendicular to the direction of the light beam. The pyramid can } \\
\text { be reoriented in any direction within the light beam. Under these conditions, which } \\
\text { one of the shadows } \mathbf{P}, \mathbf{Q}, \mathbf{R} \text {, and } \mathbf{S} \text { is NOT possible? }\end{array}$ \\
\hline Opaque \\
pyramid
\end{tabular}