Which is not an object? string list dictionary None of the above code example

Example: Create a data dictionary of 5 states having state name as key and number python 3

city_population = {"New York City": 8550405, 
                   "Los Angeles": 3971883, 
                   "Toronto": 2731571, 
                   "Chicago": 2720546, 
                   "Houston": 2296224, 
                   "Montreal": 1704694, 
                   "Calgary": 1239220, 
                   "Vancouver": 631486, 
                   "Boston": 667137}
city_population["New York City"]