Harry is a project manager of a software development project. In the early stages of planning, he and the stakeholders operated with the belief that the software they were developing would work with their organization's current computer operating system. Now that the project team has started developing the software it has become apparent that the software will not work with nearly half of the organization's computer operating systems. The incorrect belief Harry had in the software compatibility is an example of what in project management?

A. Issue
B. Risk
C. Constraint
D. Assumption