单项选择题

W: There are many interesting stories about how a baby learns to say its first word. Now, Mark, would you like to share your story with us
M: OK, here is my story. I was about 18 months old, I think. And I had just started saying my first word. Every time a truck went by, I shouted a word that sounded like "truck", but to everyone else it sounded nothing like it. My parents tried to correct me, but failed. Then about 3 months later, we traveled to New York.
As we were waiting for our plane at the airport, I looked out of a huge window. At that very moment, I saw the largest truck in the world. I had to tell someone about this. I turned to my father, who was standing next to about a thousand people waiting for flight, and screamed "Truck! Truck!" My father tried hard to shut me up, but I was so excited and I kept screaming my special word. My poor mother decided that she didn’t know this baby and ran to the lady’s room where she hid until I finally stopped. Well, I was talking like a normal child. However, my parents will never forget the very first word I produced in my life.

What is the first word the baby to say()

A. Truck.
B. OK.
C. Duck.