19

Do you know that Britain was part of the Roman Empire for over three and a half centuries? From the invasion in AD 48 until rule from Rome ended in the 5th century, the province of Britannia was part of a political union that covered most of Europe.
«union that covered most of Europe» - союз, охвативший большую часть Европы (most - большенство) (Степани сравнения)

MUCH

20

This period was marked by several key events, both military and civilian.
«This period was marked» - Этот период был отмечен (тогда в прошлом) (Past Simple Passive)

MARK

21

By the early 5th century, the Roman Empire could no longer defend itself against either internal rebellion or the external threat posed by Germanic tribes expanding in Western Europe. The last of the Roman troops left Britain.
«Empire could no longer defend itself against» - Империя больше не могла защитить (сама) себя от (Pronouns - местоимения)

IT

22

Hadrian’s Wall was the north-west frontier of the Roman empire for nearly 300 years. It was built by the Roman army on the orders of the emperor Hadrian following his visit to Britain in AD 122.
«It was built by the Roman army on the orders of the emperor Hadrian following his visit to Britain in AD 122. » (following – следующий, предшествующий) (Participle I - причастие )

FOLLOW

23

By about AD 100 there were many Roman forts in the north of Britain. The forts here were linked by a road, now known as the Stanegate, between Corbridge and Carlisle.
«The forts here were linked» - Форты здесь были связаны (тогда в прошлом) (Past Simple Passive)

LINK

24

Hadrian came to Britain in AD 122 and, according to a biography written 200 years later, ‘put many things to right and was the first to build a wall 80 miles long from sea to sea te separate the barbarians from the Romans’.
«according to a biography written 200 years later» - Согласно биографии, написанной 200 лет спустя (Participle II - – пассивное причастие)

WRITE