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II. Раскройте
скобки, употребляя глагол в Past Continuous.

A. What was happening (happen) at the time of
the robbery?

B. Well, I ____ (sit) in my office. I
__________________ (talk) to an employee. Mary ______ (put) food onto the
shelves. Several customers ______ (do) the shopping and a cashier ______
(stand) behind the till.

A. Can you tell me anything about the robbers?

B. Yes. They _____ (wear) black masks and
they  (hold)  guns. They ______ (shout).

A. How did they get away?

B. They drove off  in a car which  ______________________ (wait) outside.

здесь же не трудно. В Past Continuous просто надо каждый глагол писать в форме was + окончание ing (если имя существительное в единственном числе)  или  were + ing (если в множественном). В документе всё написано.