[alittle2407]

My daughters chemistry teacher marked the following question as incorrect - see attached image.

I think the terms are incorrect - "Unburnt gas" will be travelling through the chimney of the bunsen burner and arriving at B where it will promptly be "burned".
If the air hole was closed and it was a yellow flame there may be unburnt hydrocarbons released at the top of the flame.
But the question says "roaring flame" so surely the answer must be B.

What does everyone else think?

Andrew

[Dan]

The correct answer is B. The teacher is wrong.