Christian was very nervous about his first day of school. He was new to the city of chicago and he wasn’t sure what to expect. What if he wasn’t able to make any new friends? Christian was worried. “Don’t worry,” said his mother, “You are a nice boy and I am sure that you will make new friends.” Christian replied, “But I liked my friends in Ohio. I don’t want to make new friends!” When the school bus came, Christian walked out the house sadly. He board the bus and sat in the last empty seat. The girl sitting next to him said, “Hello. My name is Laila. I just moved here from Ohio last week. What is your name?” Christian smiled and said, “My name is Christian and I’m from Ohio too!” Christian and Laila talked about all the fun things they used to do in Ohio. Christian was relieved that he made a new friend after all.

What is the plural form of the underlined word "city" in the above passage?