3) they, visiting, their, grandad, were, in, the, morning, ?

Решение:

Составляем вопросительное предложение. Необходимо использовать глагол 'were visiting' (навещали) и указать, кого и когда навещали.

1. Were they visiting their grandad in the morning?

Ответ: Were they visiting their grandad in the morning?