Final answer:
Mass transit provides steady, practical transportation for millions of people.
Step-by-step explanation:
Out of the options provided, the most important feature of modern urban mass transit is that it provides steady, practical transportation for millions of people. Mass transit systems such as buses, trains, and subways offer a reliable means of transportation for commuters, reducing congestion on roads and promoting sustainability. These systems are designed to efficiently move large numbers of people, improving accessibility and reducing the reliance on individual vehicles.
Learn more about Features of modern urban mass transit