2. They (not visit) that museum before.

Задание 2. They (not visit) that museum before.

Снова Present Perfect negative. Подлежащее 'They' требует вспомогательного глагола 'have'. Третья форма глагола 'visit' — 'visited'.

Получаем:

They have not visited that museum before.

Ответ: have not visited