This sentence should read as follows. Mexico City now stands on the site of the amazing ancient capital city called Tenochtitlan.
So, your answers are A. Tenochtitlan and B. Mexico City
Hope this helps. :)
The proper nouns in the sentence are A. Tenochtitlán and B. Mexico City. These names refer to specific places. The other options are common nouns and not proper nouns.
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