13. John _______ (not play) the violin since he was school.

Решение:

Фраза 'since he was school' указывает на начало периода в прошлом. Действие (не играл на скрипке) не происходило с того момента. Используем Present Perfect, отрицательную форму.

John has not played (или hasn't played) the violin since he was at school.

Ответ: has not played