Study these sentences from the text. Then choose the correct options to complete the rules.
1. Had bicycles been an important means for many years before the advent of motorised vehicles?
2. They had played an essential role in Vietnamese daily life by the mid-20th century.
3. The motor vehicles on the roads had not increased dramatically until the 1990s.
RULES
1. The past perfect describes a past action or event that took place before / after another past action or event.
2. We form the past perfect with was / had + a past participle.
3. We use not or never to make affirmative / negative sentences.
4. The question form is auxiliary verb + subject + infinitive / past participle.