Please look at the sets of sentences, especially the last sentence in each set. I understand that all sentences in each set have the same meaning and that sentences with (*) are not grammatical. What I don’t understand is what is happening here? Can you please explain under what conditions contraction is not permitted using the examples provided?
Set #1
Mei is not happy, but I am happy.
Mei isn't happy, but I'm happy.
(*)Mei isn't happy, but I'm.
Set #2
Mei is happy in Shanghai, but she is not happy in Beijing.
Mei's happy in Shanghai, but she isn't happy in Beijing.
Mei's happy in Shanghai, but she isn't in Beijing.
Set #3
Mei is not happy in Beijing, but she is happy in Shanghai.
Mei is not happy in Beijing, but she is in Shanghai.
Mei isn't happy in Beijing, but she's happy in Shanghai.
(*)Mei isn't happy in Beijing, but she's in Shanghai.
Set #4
Mei is not in Beijing, but she is in China.
Mei isn't in Beijing, but she's in China.
Thank you so very much,
Aling