Aschool crossing sign is an example of a sign.
a. warningb. guidec. regulatory

a. warning

A school crossing sign is an example of a warning sign.

Explanation:

A warning sign is known to be a sign which shows warning about the state of the road which can be dangerous.

A school crossing sign indicate that children use or cross the road to and fro school. This sign is on the road in order to caution or alert drivers to be aware of the school children and to keep them safe.

b) to encourage free trade

one way archaeology us understand the past is through the material objects it finds, allowing us to know what was being used, and when. for example a dig recently found a flute, believed to be the oldest musical instrument found to date.

i hope this