大家好！ I have a question about the sounds -in, -ing. In what regions of China are these sounds usually distinguished? (I think it is a minority of speakers who differentiate -in from -ing, right? despite them being the standard sounds) From what I've heard, I think people from 北京 and 山东 do for sure, right? Can this distinction be found throughout 北方？ (I think in 南方 and 台湾, -ing is almost always pronounced as -in, right? except for 行) Thanks!