Middle region of flame having the colour. A. Yellow B. Black C. Red D. White

The correct answer is: White.

The middle region of a flame is called the luminous zone. It is the hottest part of the flame, and it is where the chemical reactions that produce the flame take place. The luminous zone is white because it is made up of hot gases that are emitting light.

The other options are incorrect because:

• Yellow is the color of the outer region of the flame. This region is cooler than the luminous zone, and it is where the gases that make up the flame are not as hot.
• Black is the color of the soot that is produced when the fuel in the flame is not completely burned.
• Red is the color of the inner region of the flame. This region is the hottest part of the flame, but it is not as hot as the luminous zone.

I hope this helps! Let me know if you have any other questions.