'1.' The explorer said, "We invented some kinds of anti-aging pills to help people live longer last year."
`->` The explorer said they had invented some kinds of anti-aging pills to help people live longer than the previous year.
- Câu tường thuật : S + say(s) / said or tell / told + (that) + S + V
'2.' We left the building, then a tornado appeared suddenly and caused life loss and property damage.
`->` After we had left the building, a tornado appeared suddenly and caused life loss and property damage.
- DHNB: After + S + had + VpII + O,S + V2/V-ed + O
- Thì QKHT
- Translation: Chúng tôi rời khỏi tòa nhà, sau đó một cơn lốc xoáy xuất hiện đột ngột và gây thiệt hại về người và tài sản.
'3.' A team of archeologists dug an ancient tunnel with the aid of heavy machinery. (was)
`->` An ancient tunnel was dug by a team of archeologists with the aid of heavy machinery.
- Câu bị động thì QKD
- S + was/were + VpII + (by + O)
- Translation: An ancient tunnel was dug by a team of archaeologists with the help of heavy machinery.