How can you reduce wind resistance in a warning device?

Cutting holes in the side and bottom of a warning device serves to reduce wind resistance by allowing air to flow through, rather than creating a solid barrier that the wind must push against. This design modification helps to minimize drag, as the wind can pass through the openings rather than pushing against the surfaces of the device, which could cause instability or reduce its effectiveness.

The other options involve changes that do not effectively reduce wind resistance. Adding more weight might make a device more stable but it can also increase overall drag if the device is not streamlined. Using larger materials generally increases the surface area that the wind encounters, which can lead to greater resistance rather than reducing it. Placing the device at a higher elevation might influence the way the wind interacts with it, but without altering its structure to allow airflow, it won't necessarily reduce wind resistance effectively.