Answer:
Option D. Deciding on the project manager's tittle
Step-by-step explanation:
The reason is that the composition of the project, resources required to execute a project, planning and designing of the project and deciding which strategy to implement are the key factors that decides the success of the project. Hence Option A, B and C each are one of the six key decisions in the project management.
Option D is incorrect because deciding the project manager's title doesn't any important role as it doesn't have any significant impact on the productivity of the project manager. Hence Option D is not one of the six key decisions in the project management.