Answer:
1: An event can cause changes to occur in one or more of the spheres, and/or an event can be the effect of changes in one or more of Earth's four spheres.
2This two-way cause and effect relationship between an event and a sphere is called an interaction. Interactions also occur among the spheres.
3.The OECD defines global events as events of a limited duration that have a global reach, require significant public investment and have an impact on the population and built environment
