Final answer:
The sign that marks an officially designated bicycle route is a bicycle route sign. It consists of a white pictogram of a bicyclist on a green background and is used to indicate that drivers should be cautious of bicyclists on that road.
Step-by-step explanation:
The sign that marks an officially designated bicycle route is a bicycle route sign. This sign typically consists of a white pictogram of a bicyclist on a green background. It is used to indicate to drivers that they should be cautious of bicyclists while traveling on that road.
For example, the bicycle route sign may be placed along a road that has been specifically designated as a safe and preferred route for bicyclists.
Remember, it is important for drivers to be vigilant and respectful of bicyclists to ensure everyone's safety on the road.