If two Scrum Teams are added to the development of a product that previously had...

The correct answer is A, because if two Scrum Teams are added to the development of a product that previously had only one Scrum Team, the immediate impact on the productivity of the original Scrum Team is likely to decrease. This is because adding more teams may introduce some challenges and trade-offs, such as increased communication and coordination overhead, reduced alignment and cohesion, and potential conflicts or dependencies.

References: [Suggested Reading for Professional Scrum Master™ I]