Gulliver is not able to respond to Pedro de Mendez's help because

The choices can be found elsewhere and as follows:

de Mendez has been an old enemy
de Mendez quarantines Gulliver from the sailors

I believe the answer is the first one. Gulliver is not able to respond to pedro de mendez's help because de Mendez has been an old enemy.

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polisit can also mean a body of citizens. in modern historiography, polis is normally used to indicate the ancient greek city-states, like classical athens and its contemporaries, and thus is often translated as "city-state". the body of citizens came to be the most important meaning of the term polis in ancient greece.