I...when suddenly dog began to bark. study studied was studying изберите

I ... when suddenly dog began to bark. 1) study; 2) studied; 3) was studying Past continuous tense - прошедшее долгое время (прошлое действие, которое в процессе было прервано другим прошедшим действием).

I was studying when suddenly dog began to bark. - Я обучался, когда вдруг собака начала лаять.