Your answer should be WHO.
Think of it like this: You wouldn't say "The boy it (a variant of 'which')", because it simply just sounds odd. Instead, you're wired to think "The boy, he (an unknown name, so it would be 'who')".
The exact noun for children is child.
key:
f/n = friends name
y/n = your name
Dear f/n,
I am writing you to inform you that I will be joining the ____ club at our school! I really like the whole concept of it, and maybe we could even join together? I just wanted to let you know in advance.
Kind regards,
y/n
(i don necessarily know why your sending this letter, so if you need anything changed, let me know!!)
Flabbergast means that you are shocked for example "I am flabbergasted". It relates to weary and hesitant because those two words relate to being shocked.
