Hi,
you can tell me if what i write is, if there are no mistakes? you.
dear mrs murray,
i am writing to apply for a job as a dog walker.
i am 14 years old and i am a student at stevens school. i love animals. i have three cats, two dogs and a rabbit.
i'm free all weekend and i live in manchester.
later, i would like to study to become a veterinary, that's my ambition.
last summer i worked for four weeks at the shop "toutounet."
and four other week at the spa, i enjoyed.
every night, i'll walk the dog of my neighbor because she is elderly.
i am a nice person and i love meeting people.
my phone number is (020) 85541254 and my mobile number is 077765015841.
yours sincerely,

This is how I would write it:
Dear Mrs. Murray,
I am writing to apply for a job as a dog walker. I am 14 years old and I am a student at Stevens school. I just adore animals. I have three cats, two dogs and a rabbit, which makes me experienced in animal care. I live in Manchester and the hours I can work are all day on weekends. Last summer I worked for four weeks at the shop "Toutounet"' and four other weeks at the spa. I enjoyed working there, but I would rather work with animals because someday I would like to study to become a veterinary, for that is my ambition. Every night, I walk the dog of my neighbor because she is elderly and not able to do much. I am a nice person and I love meeting people. My phone number is (020) 855-412-54 and my mobile number is 077765015841. I hope to see you and your dog soon!
Yours sincerely, 
Pandamille

I believe the answer is B :)