Can 'is' and 'are' coexist in a same sentence?

[Sonubajwa2003]

However, how effective these new measures, put in place by the European Union and the United States, are is a question that only time can answer!

Is it correct?

[Kitosdad]

Good morning Sonubajwa2003, definitely a question for the grammarians amongst us.

Personally I can read and understand the sentence without problem, but I feel that a comma after the "are" would probably make it a lot clearer to non-native speakers.

"However, how effective these new measures, put in place by the European Union and the United States are, is a question that only time can answer!"

Kitos.
_________________
Keep it simple ... Keep it interesting.

[Alan]

HI,

I agree with the position of the comma since 'are is' sounds very odd. I'm not too happy about the juxtaposition of 'however' and 'how'.

I would suggest:

Nevertheless, how effective the (these) new measures put in place by the European Union and the United States are, remains a question that only time can answer.

Offered in all humility!

Alan
_________________
English as a Second Language
You can read my ESL story Present Simple