Structure of the interrogative sentence

Hello,

I tested “Language Tool” for this sentence:

Why are Dave and his wife arguing?

The corrector proposes me “is”.

I would like to know a little more about my error.

Thank you very much of your help.

You can analyze the problem here:

Text Analysis - LanguageTool?

“Dave” is detected as a singular noun phrase instead of “Dave and his wife” being detected as a plural noun phrase. The problem is in our Java class EnglishChunkFilter, where we don’t yet accept the “and” to form plural noun phrases, as this caused false alarms of other sorts. Help with improving this is very welcome.