A business analyst (BA) is planning how to present a set of requirements for a...

 The requirements attribute that the BA should assign to allow cost implications to be assessed is complexity. This is because complexity is a measure of how difficult, intricate, or involved a requirement or a solution is. Complexity can have an impact on the cost of implementing or maintaining a requirement or a solution by affecting the effort, time, resources, or skills needed. Assigning complexity to the requirements can help to estimate and compare the cost implications of different requirements or solutions, especially for a project with financial constraints. The other options are not as relevant or useful as complexity. References:

BABOK Guide, section 4.2.4: Structure Requirements

CCBA Practice Test, question 109