In the diagram, which letter represents the transition from liquid to gas?

B

A

D

C

I got on here because I don't understand the question but I did my best to answer because I noticed you asked 3 days ago. IF I'm right the answer is D. My diagram shows

A at - 50 °C

B at 0 °C

C at 50 °C

D at 100 °C (gas to liquid or liquid to gas)

And E at 150 °C

So I hope I'm right because I'm answering the same question.