Which sign indicates that cyclists may be present on the road?

Answer: C — Bicycle warning sign

The correct choice indicates the presence of cyclists on the road through a specific warning sign intended to alert other road users. A bicycle warning sign typically features a graphic representation of a bicycle. This serves as a clear visual cue to drivers and pedestrians that bicycles may be on the road, prompting them to be more vigilant. This sign enhances safety by encouraging drivers to share the road responsibly with cyclists, as unexpected interactions can lead to accidents or unsafe situations. It is particularly important in areas where cyclists frequently share the roadway with motor vehicles, such as in urban areas or near parks. The other options do not effectively communicate the potential presence of cyclists. A bicycle lane only signifies a dedicated lane for cyclists, while cyclist activity warning is a more general indication and may not be as universally recognized. A sign stating road closed to bicycles clearly restricts cyclists rather than warning of their presence.