帮忙找范文why people want tolearn a foreign language

What is it about foreign that isn't quite right?
I want to know what it is about foreigner's Chinese that makes it still sound foreign.Someone mentioned that even Da Shan,who supposedly has excellent Chinese for a foreigner,still has a hint of ...something.What is it that gives away that he is not native Chinese if you were to only hear his voice?
What are some...
sounds
words
intitial
finals
combinations
tones
whatever else
...that foreigners never seem to get quite right?