NOTE: Questions 16-19 are under the one Category of Cement Production.

There are four different zones in a burning kiln (before cooling): 

• Dehydration zone
• Calcination zone
• Solid-state reaction zone
• Clinkering zone.

After the rapid cooling process, this process creates the four main cement minerals: 

• C3S
• C2S
• C4AF
• C3A

Which zone is involved in the largest CO2 emission during the cement clinkering production? Select the correct answer from the list (2 marks)