updated practice questions

exams/extras.md

@@ -91,6 +91,10 @@ Explain the following terms used in agile development:
 
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+How can the **Black Sheep Effect** impact team behaviour?
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 What is "Docker"?
 
 Explain the purpose of the relationship between **Docker Engine**, **Docker Compose** and **Docker Machine**.
@@ -196,18 +200,6 @@ Define and explain three types of cloud services.
 
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-Explain how a server load balancer works
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-Explain how a server cluster works
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-Explain, with the aid of a diagram, the principles behind server virtualisation.
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-List two benefits of employing virtualisation.
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 Continuous Integration and Continuous Deployment are often used by software development teams. For each of these:
 
 1. Explain the process