What do class/group abbreviations stand for?

Hello everybody I hope you are doing great with ya English learning. I have just finished induction and to be honest I got interested in Let's master English courses. One thing I didn't catch was those abbreviations ( DDM/ LME/ PIRF) I would be pleased if anyone explained to me what they actually stand for? Thank in advance.

16 comments

What do class/group abbreviations stand for?