Question:
Below is a drawing of all $26$ letters in the English alphabet. As drawn below, some of these letters could be portions of the graph of a function, and some cannot. For example, the $\textsf{O}$ resembles an ellipse, which cannot be part of the graph of a function.

As drawn below, which of these letters could be portions of the graph of a function? (You may not rotate them.)

Give your answer as a list of letters with no spaces or other punctuation between them, in alphabetic order.

$$\begin{array}{c c c c c}
\textsf{A} & \textsf{B} & \textsf{C} & \textsf{D} & \textsf{E}\\\\
\textsf{F} & \textsf{G} & \textsf{H} & \textsf{I} & \textsf{J}\\\\
\textsf{K} & \textsf{L} & \textsf{M} & \textsf{N} & \textsf{O}\\\\
\textsf{P} & \textsf{Q} & \textsf{R} & \textsf{S} & \textsf{T}\\\\
\textsf{U} & \textsf{V} & \textsf{W} & \textsf{X} & \textsf{Y}\\\\
&& \textsf{Z} &&
\end{array}$$

Answer:
To be part of the graph of a function, a figure must have at most one point of intersection with any vertical line. Only two letters (as drawn in the problem) have this property: $\textsf{V}$ and $\textsf{W}.$ (Following the instructions, your answer should be formatted as $\boxed{\text{VW}}.$)