Changing membership

Hello Amia,

Thank you for your interest in Scrum.org. We're glad to learn you've been making use of our free practice assessments. We believe you may be misunderstanding the way correct answers are displayed. The answer to this question is:
C) As needed, while taking into account a short term reduction in productivity.

The feedback you are given for this Open Assessment Question is:
Teams typically go through some steps before achieving a state of increased performance. Changing membership typically reduces cohesion, affecting performance and productivity in the short term.

I hope we were able to address your inquiry. We wish you the best of luck in your continued studies.

I know what is correct answer. I want to know the source of it. Where can I read about it in Scrum Guide?

The Scrum Guide says that "Development Teams are structured and empowered by the organization to organize and manage their own work. The resulting synergy optimizes the Development Team’s overall efficiency and effectiveness".

Since a change in membership might affect the synergy referred to, it would be prudent to take into account a short term reduction in productivity.

What does it mean by changing the membership? Is it changing the roles of developers in the team or change the number of developers in the team?

I am bit confuse on this, as I saw one question during mock practice, which says:

'New members can be added during the sprint as required' - and the answer for this is FALSE.

Thanks,

Arpit

I feel this question from open assessment is quite ambiguous. Team membership should be out of scope as long as the team is cross functional and self organizing within. 

Short term reduction in productivity: Does this mean we are replacing the current developers with some new developers?

It means any change in team membership. This could knock them back at least one stage in the Tuckman model, even if only temporarily.