C. When Mary was 7 years old, 1) she went to school and learnt to write. 2) she wrote a letter to Ded Moroz. 3) she and her parents visited Veliky Ustyug.

According to the text, "When Mary was seven, her parents taught her to write and she also wrote a letter to Ded Moroz." Based on this, the correct answer is: 2) she wrote a letter to Ded Moroz. Русский перевод: Согласно тексту: "Когда Мэри было семь лет, родители научили ее писать, и она также написала письмо Деду Морозу." Исходя из этого, правильный ответ: 2) она написала письмо Деду Морозу.