Four lightweight cylinders, $W$, $X$, $Y$, and $Z$, are suspended horizontally from their midpoints by insulating nylon threads so that they are free to pivot.

• Cylinder $W$ is a metallic cylinder with a net positive charge.
• Cylinder $X$ is a metallic cylinder that is electrically neutral.
• Cylinder $Y$ is a plastic cylinder that is electrically neutral.
• Cylinder $Z$ is a metallic cylinder with a net negative charge.

A student rubs a polythene rod with a woollen cloth, giving the rod a net negative charge. She then brings this negatively charged rod near one end of each cylinder in turn.

Which of the cylinders will experience a force of attraction when the negatively charged rod is brought near?