Which of the following north american cities is not one of the 20 largest in the world?
a. new york city
b. mexico city
c. los angeles
d. chicago

The north american city that's not considered as one of the 20 largest city in the world would be:  D. chicago

New york city is the 2nd largest city in the world, Mexico city is the 3rd largest city in the world and Los Angeles is the 5th Largest city in the world.

With only 2.7 million population, Chicago is ranked 114th in the world's largest cities ranking.