2. The cooks ______ (work) in the kitchen all day long.

The question asks to complete the sentence by filling in the blank with the correct verb form. The word in parentheses indicates the base verb to be used, which is 'work'. The phrase 'all day long' suggests a continuous action in the past. Therefore, the past continuous tense of 'work' is appropriate. Kratkoe poyasnenie: Proshloye nepreryvnoye vremya ispol'zuyetsya dlya opisaniya deystviy, kotoryye prodolzhayutsya v techeniye opredelennogo perioda v proshlom. Poshagovoye resheniye:

1. Shag 1: Opredelite vremya i aspekt deystviya. Predlozheniye ukazyvayet na deystviye, kotoryye prodolzhalos' ves' den' v proshlom.
2. Shag 2: Sformiruyte proshloye nepreryvnoye vremya ot glagola 'work'. Dlya etogo ispol'zuyetsya 'was/were' + glagol s okonchaniyem '-ing'. V dannom sluchaye, 'cooks' yavlyayetsya mnogoy chislo, poetomu ispol'zuyetsya 'were working'.

Otvet: were working