It is thought that the pyramids of Giza were constructed over 4,500 years ago.
The pyramids of Giza are thought to have been constructed over 4,500 years ago.
The Great Wall of China is known for being the longest wall in the world.
It is known that the Great Wall of China is the longest wall in the world.
The chef should be baking the cookies.
The cookies should be being baked by the chef.
It is believed that the human brain is the most complex organ in the body.
The human brain is believed to be the most complex organ in the body.
The manager could be reviewing the report.
The report could be being reviewed by the manager.
The students should have taken the exam.
The exam should have been taken by the students.
The earliest form of currency is [think + be] cowry shells, which were used thousands of years ago as a medium of exchange.
The earliest form of currency is thought to have been cowry shells, which were used thousands of years ago as a medium of exchange.
Paying more attention could have avoided the mistake.
The mistake could have been avoided by paying more attention.
The maid might be cleaning the house.
The house might be being cleaned by the maid.
The mysterious Nazca Lines of Peru [think + create] by the Nazca people between 500 BCE and 500 CE.
The mysterious Nazca Lines of Peru are thought to have been created by the Nazca people between 500 BCE and 500 CE.
The Statue of Liberty is known for being a symbol of freedom and democracy.
It is known that the Statue of Liberty is a symbol of freedom and democracy.
The oldest fossils [think + find] date back to nearly 3.5 billion years.
The oldest fossils are thought to have been found date back to nearly 3.5 billion years.
The student should be reading the book.
The book should be being read by the student.
Jupiter [think + form] very early, only a few million years after the formation of the sun.
Jupiter is thought to have been formed very early, only a few million years after the formation of the sun.
The legendary city of Atlantis [think + be] a real place, but its existence has never been proven.
The legendary city of Atlantis is thought to have been a real place, but its existence has never been proven.
The team should be playing the game.
The game should be being played by the team.
The book *that he was reading* was borrowed from the library.
The book being read by him was borrowed from the library.
The mechanic could be repairing the car.
The car could be being repaired by the mechanic.
The Taj Mahal is known for being a symbol of love and devotion.
it is known that the Taj Mahal is a symbol of love and devotion.
The artist must be creating the painting.
The painting must be being created by the artist.
The car *that the mechanic was repairing* belonged to a famous celebrity.
The car being repaired by the mechanic belonged to a famous celebrity.
It is believed that the universe is expanding at an accelerating rate.
The universe is believed to be expanding at an accelerating rate.
The recipient must have received the letter.
The letter must have been received by the recipient.
The team must be completing the project.
The project must be being completed by the team.
It is believed that the Mona Lisa was painted by Leonardo da Vinci.
The Mona Lisa is believed to have been painted by Leonardo da Vinci.
The house *that the workers were painting* looked brand new.
The house being painted by the workers looked brand new.
They might have delivered the pizza already.
The pizza might have been delivered already.
The cake *that the children were eating* was made with organic ingredients.
The cake being eaten by the children was made with organic ingredients.
It is thought that the first Olympic Games were held in ancient Greece.
The first Olympic Games are thought to have been held in ancient Greece.
The journalist might be writing the article.
The article might be being written by the journalist.
The Colosseum in Rome is known for being one of the greatest ancient amphitheaters in the world.
It is known that the Colosseum in Rome is one of the greatest ancient amphitheaters in the world.
The band must be rehearsing the song.
The song must be being rehearsed by the band.
The first written words in human history [think + develop] by the ancient Sumerians in Mesopotamia.
The first written words in human history are thought to have been developed by the ancient Sumerians in Mesopotamia.
The Eiffel Tower is known for being a symbol of Paris, France.
It is known that the Eiffel Tower is a symbol of Paris, France.
The Great Pyramids of Giza [think + build] by tens of thousands of workers over a span of 20 years.
The Great Pyramids of Giza are thought to have been built by tens of thousands of workers over a span of 20 years.