Определим тип задания: вставить пропущенное слово в предложение.
Выберем протокол К (Контекстный выбор).
- Подставим варианты ответов в предложение:
- After a heart attack, he needed a major surgery, but fortunately the operation was happy.
- After a heart attack, he needed a major surgery, but fortunately the operation was different.
- After a heart attack, he needed a major surgery, but fortunately the operation was successful.
- After a heart attack, he needed a major surgery, but fortunately the operation was personal.
Наиболее подходящим является вариант C) successful (успешная).
Ответ: C) successful