Здравствуйте, объясните, пожалуйста, почему в данных предложениях именно такие формы глаголов?

[email protected] в категроии Английский язык, вопрос открыт 18.07.2018 в 17:51

Every year patriotic songs are heard everywhere in the usa on July 4.

Many questions were answered by the president at his annual conference last Thuesday.

The candeles were lighting on the birthday cake when Sam returened from work.

P.S. Заранее спасибо!