Which of the following should be considered the biggest risk to the schedule when trying...

In the context of a system with a large GUI front end, the biggest risk to the schedule when implementing formal scripted test cases early in the SDLC is the potential need for test maintenance due to changes in the presentation layer. This is because the GUI is often subject to change, especially in the early stages of development, as feedback is received and design adjustments are made. These changes can render early test scripts obsolete, requiring updates and maintenance, which can be time-consuming and delay the testing schedule.