Final answer:
Long-term planning usually encompasses a period of at least 5 years. This is because it allows for strategic decisions that consider the potential changes in costs, market conditions, and technological advances over time.
Step-by-step explanation:
Long-range planning typically involves considering a time frame beyond immediate operational concerns or short-term strategies. In many contexts, especially in business and governmental policy, long-term planning is crucial for sustainability and strategic success. This type of planning accounts for variables that can significantly alter outcomes over extended periods, such as inflation, technological changes, and shifting market conditions.
To categorize different spans of planning periods: a plan covering anything beyond a year could be seen as long-term, but typically, long-term planning is associated with periods of five years or more. Land use and conservation efforts, as well as long-term economic and production decisions within a company, exemplify areas where long-term planning is necessary to adapt to changing circumstances and manage all variable costs effectively.
Hence, when addressing the question of the appropriate time span for long-range planning, the correct answer is c. 5 years.