Choose the correct letter, A, B or C. What is her son’s given name?

(Katrine=K Sherry=S)
K: Good moming. You must be Sherry Peters. My name’s Katrine.
S: Yes, hello. I’m Sherry Peters. Nice to meet you.
K: You have a 10 o’clock appointment with us.
S: That’s right. I’m supposed to go to the Admissions Office. Is that here?
K: Yes, it is. Please take a seat as I have several forms for you to fill in to enable you to enrol your son at this school. We have a form for your name, address and so on, one for the health of your son, and one for him to choose extra subjects to join in.
S: Thank you.
K: Now, firstly, this form is just so we have a record of your son’s personal details. Can you fill it in for me?
S: Yes, I’ll do that now.
K: Can I just check the details with you? Your son’s first name is William.
S: No, that’s his middle name, after his father, Jason William. My son’s name is Colwin. You please spell it C-O-W-I-N, not C-O-L-W-Y-N, as some people do.
K: Yes, I’ll make a note of that. And how old is Colwin?
S: I’ve put down that he’s entering Year 5, so therefore he’s 10 years old, turning 11 this year.
K: So at the moment he’s 10.
S: Yes, correct.