Long ago, when cars were not yet invented, people in the USA traveled by train or in wagons pulled by animals. There were plenty of railroad tracks in both the east and west, but they didn't connect in the center of the country, and so the national railroad network was 29 FINISHED

Выполним задание в соответствии с Протоколом А.

1. Определим орфограмму. В данном случае необходимо образовать подходящую форму слова FINISHED.
2. Кратко сформулируем правило. Необходимо образовать форму страдательного причастия прошедшего времени.
3. Разберем слово FINISH.

Т.к. в задании необходимо образовать форму страдательного причастия прошедшего времени, то слово приобретает вид FINISHED.

В итоге получаем предложение: Long ago, when cars were not yet invented, people in the USA traveled by train or in wagons pulled by animals. There were plenty of railroad tracks in both the east and west, but they didn't connect in the center of the country, and so the national railroad network was FINISHED.

Ответ: finished