"Fertile," as in fertile soil or fertile land, means that the soil and land is rich in nutrients for plants, and therefore is good for farming crops.
The stage that involves the change and adaptation of a system is upkeep and maintenance.
Developing a new system is a complex process that requires multiple steps and stages. The most important stages are:
- Planning.
- Design.
- Development.
- Testing.
- Upkeep and maintenance.
From these stages, the last one "upkeep and maintenance" is the one that requires adapting the new system that has been already designed. This is the last stage because even after testing the system it is likely this has to be fixed or adapted, the most common reasons are:
- Fails that were not detected during testing.
- Upgrading the sytem.
- Including new features to meet customers' needs.
Based on this, the phase during which the system is fixed or adapted is the upkeep and maintenance stage.
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The Spanish borderlands were located from present-day Florida to present-day California.