I want to test the ability of students to read a passage and answer questions about it. Could you please come up with a good question for the passage "Six of the seven lines of the commuter rail system, Metrolink, run out of Downtown Los Angeles, connecting Los Angeles, Ventura, San Bernardino, Riverside, Orange, and San Diego counties with the other line connecting San Bernardino, Riverside, and Orange counties directly."? 

Orange is one of a group of?