Answer & explanation
The principles underlying agile development are:
1. Individual and interactions over processes and tools.
Individual skills are considered as every team person knows what everyone is doing in the task which makes it easier to focus on development of software.
2. Maximum time is dedicated on developing and maintaining documentation. Time is invested to develop and test the code.
3.Customers are able to interact and give their response to agile developers whilst they are still busy with the development which makes it easier to know what to include in a system contract.
4. Responding to change over following a plan , it more efficient in responding to changes.