What is a characteristic of the blue-green upgrade deployment strategy?

Question:
What is a characteristic of the blue-green upgrade deployment strategy?

• A new environment is created with the new code in it, while the old environment is held in reserve in case users experience problems.
• The code changes are periodically rolled out in such a way that they do not impact current users.
• The new code is deployed all at once to the old environment. If users experience no issues, it is then moved to the new environment.
• The new code version is first rolled out to a subset of users. Changes can then be rolled back if the users experience any problems.

Exam with this question: DevNet Associate (v1.0) – Module 6 Exam Answers