1, tone sandhi: shu ǐ ng (shu ǐ ng): Up, bright, dignified, bouncing, falling, and so on are all the fourth tones.
2. Different pronunciation methods: Li (√): the fourth tone, flat tongue, close to the upper gum, air flow from the mouth, making a clear sound, play (f): the fourth tone, flat tongue, close to the upper gum, air flow from the mouth, making a clear sound.